diff --git a/config.lib b/config.lib
index 234f9e7484..9bbd86093d 100644
--- a/config.lib
+++ b/config.lib
@@ -1181,7 +1181,7 @@ make_compiler_cflags() {
 			# GCC 4.2+ automatically assumes that signed overflows do
 			# not occur in signed arithmetics, whereas we are not
 			# sure that they will not happen. It furthermore complains
-			# about it's own optimized code in some places.
+			# about its own optimized code in some places.
 			flags="$flags -fno-strict-overflow"
 			ldflags="$ldflags -fno-strict-overflow"
 		fi
diff --git a/os/debian/changelog b/os/debian/changelog
index 17958873ad..50e51ed520 100644
--- a/os/debian/changelog
+++ b/os/debian/changelog
@@ -216,7 +216,7 @@ openttd (0.6.0-2) unstable; urgency=low
   [ Matthijs Kooijman ]
   * Don't install anything into ~ during make install, this prevented
     successful builds on some architectures. Fix imported from upstream.
-  * Put the homepage in it's own Homepage field instead of in the description.
+  * Put the homepage in its own Homepage field instead of in the description.
   * Bump Standards-Version to 3.7.3
 
  -- Jordi Mallach <jordi@debian.org>  Thu, 03 Apr 2008 00:07:10 +0200
diff --git a/src/ai/api/ai_error.hpp b/src/ai/api/ai_error.hpp
index 44e36405f2..c810e57ac3 100644
--- a/src/ai/api/ai_error.hpp
+++ b/src/ai/api/ai_error.hpp
@@ -154,7 +154,7 @@ public:
 	static AIErrorType StringToError(StringID internal_string_id);
 
 	/**
-	 * Map an internal OpenTTD error message to it's NoAI equivalent.
+	 * Map an internal OpenTTD error message to its NoAI equivalent.
 	 * @note DO NOT INVOKE THIS METHOD YOURSELF! The calls are autogenerated.
 	 * @param internal_string_id The OpenTTD StringID used for an error.
 	 * @param ai_error_msg The NoAI equivalent error message.
@@ -162,7 +162,7 @@ public:
 	static void RegisterErrorMap(StringID internal_string_id, AIErrorType ai_error_msg);
 
 	/**
-	 * Map an internal OpenTTD error message to it's NoAI equivalent.
+	 * Map an internal OpenTTD error message to its NoAI equivalent.
 	 * @note DO NOT INVOKE THIS METHOD YOURSELF! The calls are autogenerated.
 	 * @param ai_error_msg The NoAI error message representation.
 	 * @param message The string representation of this error message, used for debug purposes.
diff --git a/src/ai/api/ai_gamesettings.hpp b/src/ai/api/ai_gamesettings.hpp
index 17f3c7847d..4be80c40c2 100644
--- a/src/ai/api/ai_gamesettings.hpp
+++ b/src/ai/api/ai_gamesettings.hpp
@@ -44,7 +44,7 @@ public:
 	 * @param setting The setting to check for existence.
 	 * @warning Results of this function are not governed by the API. This means
 	 *          that a setting that previously existed can be gone or has
-	 *          changed it's name.
+	 *          changed its name.
 	 * @note Results achieved in the past offer no gurantee for the future.
 	 * @return True if and only if the setting is valid.
 	 */
@@ -57,7 +57,7 @@ public:
 	 * @warning Results of this function are not governed by the API. This means
 	 *          that the value of settings may be out of the expected range. It
 	 *          also means that a setting that previously existed can be gone or
-	 *          has changed it's name/characteristics.
+	 *          has changed its name/characteristics.
 	 * @note Results achieved in the past offer no gurantee for the future.
 	 * @return The value for the setting.
 	 */
diff --git a/src/ai/api/ai_rail.hpp b/src/ai/api/ai_rail.hpp
index 5a8a3d111a..8072482438 100644
--- a/src/ai/api/ai_rail.hpp
+++ b/src/ai/api/ai_rail.hpp
@@ -406,7 +406,7 @@ public:
 	 * @pre AIMap::DistanceManhattan(tile, front) == 1.
 	 * @param tile The tile that might have a signal.
 	 * @param front The tile in front of 'tile'.
-	 * @return The SignalType of the signal on 'tile' with it's front to 'front'.
+	 * @return The SignalType of the signal on 'tile' facing to 'front'.
 	 */
 	static SignalType GetSignalType(TileIndex tile, TileIndex front);
 
diff --git a/src/ai/api/ai_tunnel.cpp b/src/ai/api/ai_tunnel.cpp
index 71b700e9b1..911b4a6fd8 100644
--- a/src/ai/api/ai_tunnel.cpp
+++ b/src/ai/api/ai_tunnel.cpp
@@ -25,7 +25,7 @@
 {
 	if (!::IsValidTile(tile)) return INVALID_TILE;
 
-	/* If it's a tunnel alread, take the easy way out! */
+	/* If it's a tunnel already, take the easy way out! */
 	if (IsTunnelTile(tile)) return ::GetOtherTunnelEnd(tile);
 
 	uint start_z;
diff --git a/src/ai/api/ai_vehicle.hpp b/src/ai/api/ai_vehicle.hpp
index 049ee8ade0..124f5a7385 100644
--- a/src/ai/api/ai_vehicle.hpp
+++ b/src/ai/api/ai_vehicle.hpp
@@ -314,7 +314,7 @@ public:
 	static VehicleID BuildVehicle(TileIndex depot, EngineID engine_id);
 
 	/**
-	 * Clones a vehicle at the given depot, copying or cloning it's orders.
+	 * Clones a vehicle at the given depot, copying or cloning its orders.
 	 * @param depot The depot where the vehicle will be build.
 	 * @param vehicle_id The vehicle to use as example for the new vehicle.
 	 * @param share_orders Should the orders be copied or shared?
diff --git a/src/clear_map.h b/src/clear_map.h
index f5c9271d29..881e94a6e4 100644
--- a/src/clear_map.h
+++ b/src/clear_map.h
@@ -322,7 +322,7 @@ static inline void MakeSnow(TileIndex t, uint density = 0)
 }
 
 /**
- * Clear the snow from a tile and return it to it's previous type.
+ * Clear the snow from a tile and return it to its previous type.
  * @param t the tile to clear of snow
  * @pre GetClearGround(t) == CLEAR_SNOW
  */
diff --git a/src/core/math_func.hpp b/src/core/math_func.hpp
index e0b9dbc89e..d57a3a511b 100644
--- a/src/core/math_func.hpp
+++ b/src/core/math_func.hpp
@@ -226,10 +226,10 @@ static FORCEINLINE int32 ClampToI32(const int64 a)
  */
 static FORCEINLINE uint16 ClampToU16(const uint64 a)
 {
-	/* MSVC thinks, in it's infinite wisdom, that int min(int, int) is a better
+	/* MSVC thinks, in its infinite wisdom, that int min(int, int) is a better
 	 * match for min(uint64, uint) than uint64 min(uint64, uint64). As such we
-	 * need to cast the UINT16_MAX to prevent MSVC from displaying it's
-	 * infinite with loads of warnings. */
+	 * need to cast the UINT16_MAX to prevent MSVC from displaying its
+	 * infinite loads of warnings. */
 	return (uint16)min<uint64>(a, (uint64)UINT16_MAX);
 }
 
diff --git a/src/debug.h b/src/debug.h
index f6e4b7bb3a..35f74c2064 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -71,7 +71,7 @@ const char *GetDebugString();
  *
  * Is the correct usage for multiple TIC() / TOC() calls.
  *
- * TIC() / TOC() creates it's own block, so make sure not the mangle
+ * TIC() / TOC() creates its own block, so make sure not the mangle
  *  it with another block.
  **/
 #define TIC() {\
diff --git a/src/economy.cpp b/src/economy.cpp
index de563910ac..41693cf13e 100644
--- a/src/economy.cpp
+++ b/src/economy.cpp
@@ -1195,7 +1195,7 @@ static void LoadUnloadVehicle(Vehicle *v, int *cargo_left)
 			payment->SetCargo(v->cargo_type);
 
 			if (HasBit(ge->acceptance_pickup, GoodsEntry::ACCEPTANCE) && !(u->current_order.GetUnloadType() & OUFB_TRANSFER)) {
-				/* The cargo has reached it's final destination, the packets may now be destroyed */
+				/* The cargo has reached its final destination, the packets may now be destroyed */
 				remaining = v->cargo.MoveTo<StationCargoList>(NULL, amount_unloaded, VehicleCargoList::MTA_FINAL_DELIVERY, payment, last_visited);
 
 				dirty_vehicle = true;
diff --git a/src/fileio.cpp b/src/fileio.cpp
index b05e5a6486..dfa3dca1da 100644
--- a/src/fileio.cpp
+++ b/src/fileio.cpp
@@ -1127,7 +1127,7 @@ void *ReadFileToMem(const char *filename, size_t *lenp, size_t maxsize)
 
 
 /**
- * Scan a single directory (and recursively it's children) and add
+ * Scan a single directory (and recursively its children) and add
  * any graphics sets that are found.
  * @param fs              the file scanner to add the files to
  * @param extension       the extension of files to search for.
diff --git a/src/fios.cpp b/src/fios.cpp
index cfaa23faf0..e58ddd9bd7 100644
--- a/src/fios.cpp
+++ b/src/fios.cpp
@@ -246,7 +246,7 @@ bool FiosFileScanner::AddFile(const char *filename, size_t basepath_length)
 	fios->type = type;
 	strecpy(fios->name, filename, lastof(fios->name));
 
-	/* If the file doesn't have a title, use it's filename */
+	/* If the file doesn't have a title, use its filename */
 	const char *t = fios_title;
 	if (StrEmpty(fios_title)) {
 		t = strrchr(filename, PATHSEPCHAR);
@@ -609,7 +609,7 @@ public:
 static ScenarioScanner _scanner;
 
 /**
- * Check whether we've got a given scenario based on it's unique ID.
+ * Check whether we've got a given scenario based on its unique ID.
  * @param ci the content info to compare it to
  * @param md5sum whether to look at the md5sum or the id
  * @return true if we've got the scenario
diff --git a/src/landscape.cpp b/src/landscape.cpp
index 6c9f062f5f..a83c42d70a 100644
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -291,7 +291,7 @@ int GetSlopeZInCorner(Slope tileh, Corner corner)
 /**
  * Determine the Z height of the corners of a specific tile edge
  *
- * @note If a tile has a non-continuous halftile foundation, a corner can have different heights wrt. it's edges.
+ * @note If a tile has a non-continuous halftile foundation, a corner can have different heights wrt. its edges.
  *
  * @pre z1 and z2 must be initialized (typ. with TileZ). The corner heights just get added.
  *
diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index ed05584cf8..47156f690d 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -47,7 +47,7 @@ void CcGiveMoney(const CommandCost &result, TileIndex tile, uint32 p1, uint32 p2
 #ifdef ENABLE_NETWORK
 	if (result.Failed() || !_settings_game.economy.give_money) return;
 
-	/* Inform the company of the action of one of it's clients (controllers). */
+	/* Inform the company of the action of one of its clients (controllers). */
 	char msg[64];
 	SetDParam(0, p2);
 	GetString(msg, STR_COMPANY_NAME, lastof(msg));
diff --git a/src/misc/binaryheap.hpp b/src/misc/binaryheap.hpp
index 7168cd03ca..65c026ac09 100644
--- a/src/misc/binaryheap.hpp
+++ b/src/misc/binaryheap.hpp
@@ -23,7 +23,7 @@
 
 /**
  * Binary Heap as C++ template.
- *  A carrier which keeps it's items automaticaly holds the smallest item at
+ *  A carrier which keeps its items automaticaly holds the smallest item at
  *  the first position. The order of items is maintained by using a binary tree.
  *  The implementation is used for priority queue's.
  *
diff --git a/src/network/core/address.h b/src/network/core/address.h
index 6385c5d02a..b20a28773a 100644
--- a/src/network/core/address.h
+++ b/src/network/core/address.h
@@ -129,7 +129,7 @@ public:
 	const char *GetAddressAsString(bool with_family = true);
 
 	/**
-	 * Get the address in it's internal representation.
+	 * Get the address in its internal representation.
 	 * @return the address
 	 */
 	const sockaddr_storage *GetAddress();
diff --git a/src/network/network_content.cpp b/src/network/network_content.cpp
index cf69e09fa6..042f4596d1 100644
--- a/src/network/network_content.cpp
+++ b/src/network/network_content.cpp
@@ -825,7 +825,7 @@ void ClientNetworkContentSocketHandler::UnselectAll()
 	}
 }
 
-/** Toggle the state of a content info and check it's dependencies */
+/** Toggle the state of a content info and check its dependencies */
 void ClientNetworkContentSocketHandler::ToggleSelectedState(const ContentInfo *ci)
 {
 	switch (ci->state) {
diff --git a/src/newgrf_industrytiles.h b/src/newgrf_industrytiles.h
index 086e6b1209..140d1b9497 100644
--- a/src/newgrf_industrytiles.h
+++ b/src/newgrf_industrytiles.h
@@ -37,7 +37,7 @@ bool StartStopIndustryTileAnimation(const Industry *ind, IndustryAnimationTrigge
 enum IndustryTileTrigger {
 	/* The tile of the industry has been triggered during the tileloop. */
 	INDTILE_TRIGGER_TILE_LOOP       = 0x01,
-	/* The industry has been triggered via it's tick. */
+	/* The industry has been triggered via its tick. */
 	INDUSTRY_TRIGGER_INDUSTRY_TICK  = 0x02,
 	/* Cargo has been delivered. */
 	INDUSTRY_TRIGGER_RECEIVED_CARGO = 0x04,
diff --git a/src/os/windows/win32.cpp b/src/os/windows/win32.cpp
index 4374307f9f..7083e37273 100644
--- a/src/os/windows/win32.cpp
+++ b/src/os/windows/win32.cpp
@@ -82,7 +82,7 @@ void ShowOSErrorBox(const char *buf, bool system)
 /* suballocator - satisfies most requests with a reusable static instance.
  * this avoids hundreds of alloc/free which would fragment the heap.
  * To guarantee concurrency, we fall back to malloc if the instance is
- * already in use (it's important to avoid suprises since this is such a
+ * already in use (it's important to avoid surprises since this is such a
  * low-level routine). */
 static DIR _global_dir;
 static LONG _global_dir_is_in_use = false;
diff --git a/src/osk_gui.cpp b/src/osk_gui.cpp
index fdd9fd1f7e..51dbd47458 100644
--- a/src/osk_gui.cpp
+++ b/src/osk_gui.cpp
@@ -465,7 +465,7 @@ void ShowOnScreenKeyboard(QueryStringBaseWindow *parent, int button, int cancel,
  * Updates the original text of the OSK so when the 'parent' changes the
  * original and you press on cancel you won't get the 'old' original text
  * but the updated one.
- * @param parent window that just updated it's orignal text
+ * @param parent window that just updated its orignal text
  * @param button widget number of parent's textbox to update
  */
 void UpdateOSKOriginalText(const QueryStringBaseWindow *parent, int button)
diff --git a/src/pathfinder/npf/queue.h b/src/pathfinder/npf/queue.h
index fc913de350..1d94ac7401 100644
--- a/src/pathfinder/npf/queue.h
+++ b/src/pathfinder/npf/queue.h
@@ -55,7 +55,7 @@ struct Queue {
 	 */
 	Queue_DeleteProc *del;
 
-	/* Clears the queue, by removing all values from it. It's state is
+	/* Clears the queue, by removing all values from it. Its state is
 	 * effectively reset. If free_items is true, each of the items cleared
 	 * in this way are free()'d.
 	 */
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
index 823e9fed0a..c97ac1b0ab 100644
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -225,7 +225,7 @@ static CommandCost RemoveRoad(TileIndex tile, DoCommandFlag flags, RoadBits piec
 				SetRoadTypes(other_end, GetRoadTypes(other_end) & ~RoadTypeToRoadTypes(rt));
 				SetRoadTypes(tile, GetRoadTypes(tile) & ~RoadTypeToRoadTypes(rt));
 
-				/* If the owner of the bridge sells all it's road, also move the ownership
+				/* If the owner of the bridge sells all its road, also move the ownership
 				 * to the owner of the other roadtype. */
 				RoadType other_rt = (rt == ROADTYPE_ROAD) ? ROADTYPE_TRAM : ROADTYPE_ROAD;
 				Owner other_owner = GetRoadOwner(tile, other_rt);
diff --git a/src/slope_func.h b/src/slope_func.h
index c90a84ff6c..b6a0a6e9d2 100644
--- a/src/slope_func.h
+++ b/src/slope_func.h
@@ -57,7 +57,7 @@ static inline bool IsHalftileSlope(Slope s)
  * Non-halftile slopes remain unmodified.
  *
  * @param s A #Slope.
- * @return The slope s without it's halftile slope.
+ * @return The slope s without its halftile slope.
  */
 static inline Slope RemoveHalftileSlope(Slope s)
 {
diff --git a/src/sound.cpp b/src/sound.cpp
index 4edfccdc2d..d54464cd4e 100644
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -115,7 +115,7 @@ static bool SetBankSource(MixerChannel *mc, const SoundEntry *sound)
 
 	int8 *mem = MallocT<int8>(sound->file_size + 2);
 	/* Add two extra bytes so rate conversion can read these
-	 * without reading out of it's input buffer. */
+	 * without reading out of its input buffer. */
 	mem[sound->file_size    ] = 0;
 	mem[sound->file_size + 1] = 0;
 
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
index 9e3e70cfae..a996ff5cd0 100644
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -221,7 +221,7 @@ struct StationNameInformation {
  * @param tile the tile to search
  * @param user_data the StationNameInformation to base the search on
  * @return true if the tile contains an industry that has not given
- *              it's name to one of the other stations in town.
+ *              its name to one of the other stations in town.
  */
 static bool FindNearIndustryName(TileIndex tile, void *user_data)
 {
@@ -768,7 +768,7 @@ static CommandCost CheckFlatLandRailStation(TileArea tile_area, DoCommandFlag fl
 				}
 			}
 		} else {
-			/* Rail type is only valid when building a railway station; in station to
+			/* Rail type is only valid when building a railway station; if station to
 			 * build isn't a rail station it's INVALID_RAILTYPE. */
 			if (rt != INVALID_RAILTYPE &&
 					IsPlainRailTile(tile_cur) && !HasSignals(tile_cur) &&
diff --git a/src/stdafx.h b/src/stdafx.h
index 25973dea6f..ccda374397 100644
--- a/src/stdafx.h
+++ b/src/stdafx.h
@@ -228,9 +228,9 @@
 #if defined(DOS)
 	/* The DOS port does not have all signals/signal functions. */
 	#define strsignal(sig) ""
-	/* Use 'no floating point' for bus errors; SIGBUS does not
-	 * exist for does, SIGNOFP not for other platforms. So it's
-	 * fairly safe the interchange those. */
+	/* Use 'no floating point' for bus errors; SIGBUS does not exist
+	 * for DOS, SIGNOFP for other platforms. So it's fairly safe
+	 * to interchange those. */
 	#define SIGBUS SIGNOFP
 #endif
 
diff --git a/src/strgen/strgen.cpp b/src/strgen/strgen.cpp
index 22450bddfe..8992ad6c64 100644
--- a/src/strgen/strgen.cpp
+++ b/src/strgen/strgen.cpp
@@ -816,7 +816,7 @@ static void ParseFile(const char *file, bool english)
 	FILE *in;
 	char buf[2048];
 
-	/* Only look at the final filename to determine whether it's be base language or not */
+	/* Only look at the final filename to determine whether it's the base language or not */
 	const char *cur_file = strrchr(_file, PATHSEPCHAR);
 	const char *next_file = strrchr(file, PATHSEPCHAR);
 	_translation = next_file != NULL && cur_file != NULL && strcmp(cur_file, next_file) != 0;
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index babc509d45..c4f10b072b 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -1657,7 +1657,7 @@ struct SpotData {
 
 /**
  * CircularTileSearch callback; finds the tile furthest from any
- * water. slightly bit tricky, since it has to do a search of it's own
+ * water. slightly bit tricky, since it has to do a search of its own
  * in order to find the distance to the water from each square in the
  * radius.
  *
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 97d44291c3..00c5d3a914 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -878,7 +878,7 @@ static void RestoreTrainBackup(TrainList &list)
 }
 
 /**
- * Remove the given wagon from it's consist.
+ * Remove the given wagon from its consist.
  * @param part the part of the train to remove.
  * @param chain whether to remove the whole chain.
  */
@@ -2815,7 +2815,7 @@ void Train::MarkDirty()
 }
 
 /**
- * This function looks at the vehicle and updates it's speed (cur_speed
+ * This function looks at the vehicle and updates its speed (cur_speed
  * and subspeed) variables. Furthermore, it returns the distance that
  * the train can drive this tick. This distance is expressed as 256 * n,
  * where n is the number of straight (long) tracks the train can
diff --git a/src/unmovable_map.h b/src/unmovable_map.h
index 72cbc37395..1b01c56376 100644
--- a/src/unmovable_map.h
+++ b/src/unmovable_map.h
@@ -256,7 +256,7 @@ static inline void MakeUnmovableHQHelper(TileIndex t, uint8 section, Owner o)
 }
 
 /**
- * Make an HQ with the give tile as it's northern tile.
+ * Make an HQ with the given tile as its northern tile.
  * @param t the tile to make the northern tile of a HQ.
  * @param o the owner of the HQ.
  */
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 822ad73994..bd016c6839 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -1142,8 +1142,8 @@ void VehicleEnterDepot(Vehicle *v)
 
 
 /**
- * Move a vehicle in the game state; that is moving it's position in
- * the position hashes and marking it's location in the viewport dirty
+ * Move a vehicle in the game state; that is moving its position in
+ * the position hashes and marking its location in the viewport dirty
  * if requested.
  * @param v vehicle to move
  * @param update_viewport whether to dirty the viewport
diff --git a/src/viewport.cpp b/src/viewport.cpp
index c9b6746056..8347c3e8b8 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -673,7 +673,7 @@ void AddSortableSpriteToDraw(SpriteID image, PaletteID pal, int x, int y, int w,
 	}
 
 	if (_draw_bounding_boxes && (image != SPR_EMPTY_BOUNDING_BOX)) {
-		/* Compute maximal extents of sprite and it's bounding box */
+		/* Compute maximal extents of sprite and its bounding box */
 		left   = min(left  , RemapCoords(x + w          , y + bb_offset_y, z + bb_offset_z).x);
 		right  = max(right , RemapCoords(x + bb_offset_x, y + h          , z + bb_offset_z).x + 1);
 		top    = min(top   , RemapCoords(x + bb_offset_x, y + bb_offset_y, z + dz         ).y);