Steal some of stepnem's typo fixing thunder.

common/content/io.js

@@ -731,7 +731,7 @@ lookup:
         }
 
         options.add(["banghist", "bh"],
-            "Replace occurences of ! with the previous command when executing external commands",
+            "Replace occurrences of ! with the previous command when executing external commands",
             "boolean", true);
 
         options.add(["fileencoding", "fenc"],

common/locale/en-US/hints.xml

@@ -31,7 +31,7 @@
     <description>
         <p>
             Start <t>QuickHint</t> mode. In this mode, every clickable
-            element (as definied by the <o>hinttags</o> option) is
+            element (as defined by the <o>hinttags</o> option) is
             highlighted and numbered.  Elements can be selected
             either by typing their number, or by typing part of
             their text to narrow down the result. When an element

common/locale/en-US/index.xml

@@ -360,7 +360,7 @@ This file contains a list of all available commands, mappings and options.
     <dt><o>activate</o></dt> <dd>Define when tabs are automatically activated</dd>
     <dt><o>altwildmode</o></dt> <dd>Define how command line completion works when the Alt key is pressed</dd>
     <dt><o>autocomplete</o></dt> <dd>Automatically update the completion list on any key press</dd>
-    <dt><o>banghist</o></dt> <dd>Replace occurences of ! with the previous command when executing external commands</dd>
+    <dt><o>banghist</o></dt> <dd>Replace occurrences of ! with the previous command when executing external commands</dd>
     <dt><o>cdpath</o></dt> <dd>List of directories searched when executing <ex>:cd</ex></dd>
     <dt><o>complete</o></dt> <dd>Items which are completed at the <ex>:open</ex> prompts</dd>
     <dt><o>defsearch</o></dt> <dd>Set the default search engine</dd>

common/locale/en-US/pattern.xml

@@ -101,7 +101,7 @@
     <tags>*</tags>
     <spec>*</spec>
     <description short="true">
-        <p>Search forward for the next occurence of the word under cursor.</p>
+        <p>Search forward for the next occurrence of the word under cursor.</p>
     </description>
 </item>
 
@@ -109,7 +109,7 @@
     <tags>#</tags>
     <spec>#</spec>
     <description short="true">
-        <p>Search backward for the previous occurence of the word under cursor.</p>
+        <p>Search backward for the previous occurrence of the word under cursor.</p>
     </description>
 </item>
 

pentadactyl/locale/en-US/intro.xml

@@ -82,7 +82,7 @@
         Selecting hyperlinks and other page elements.
     </li>
     <li>
-        <link topic="map">Keyboard shorcuts and commands</link>:
+        <link topic="map">Keyboard shortcuts and commands</link>:
         Defining new key mappings, abbreviations and user commands.
     </li>
     <li>