Fix miscellaneous spelling errors and typos.

diff --git a/documentation/documentation.sgml b/documentation/documentation.sgml
index aab9b99..4a20eba 100644
--- a/documentation/documentation.sgml
+++ b/documentation/documentation.sgml
@@ -148,7 +148,7 @@
           <listItem><para>
           Additional notes such as interaction with other parts of the system, differences
           between Wines implementation and Win32s, errors in MSDN documentation,
-          undocumented cases and bugs that Wine corrects or is compatable with.
+          undocumented cases and bugs that Wine corrects or is compatible with.
           </para></listitem>
 
           </itemizedlist>
@@ -340,7 +340,7 @@
 
           <listItem><para>
           <command>BUGS</command>. Any bugs in the function that exist 'by design', i.e.
-          those that will not be fixed or exist for compatability with Windows.
+          those that will not be fixed or exist for compatibility with Windows.
           </para></listitem>
 
           <listItem><para>
diff --git a/documentation/porting.sgml b/documentation/porting.sgml
index 603aa91..dbe78b5 100644
--- a/documentation/porting.sgml
+++ b/documentation/porting.sgml
@@ -65,13 +65,13 @@
 
         <itemizedlist>
           <listitem>
-            <para>existance of a header file</para>
+            <para>existence of a header file</para>
           </listitem>
           <listitem>
-            <para>existance of a library function</para>
+            <para>existence of a library function</para>
           </listitem>
           <listitem>
-            <para>existance of libraries</para>
+            <para>existence of libraries</para>
           </listitem>
           <listitem>
             <para>bugs in header files, library functions, the compiler, ...</para>
diff --git a/documentation/winelib-porting.sgml b/documentation/winelib-porting.sgml
index 236253d..c21dc46 100644
--- a/documentation/winelib-porting.sgml
+++ b/documentation/winelib-porting.sgml
@@ -222,7 +222,7 @@
       <para>
         In order to avoid warnings in C (and potential errors in C++)
         from not having prototypes, you may need to use a set of MS
-        compatable header files. These are scheduled for inclusion
+        compatible header files. These are scheduled for inclusion
         into Wine but at the time of writing are not available. Until
         they are, you can try prototyping the functions you need, or
         just live with the warnings.