Slight improvements to URL Fixer code

chrome/content/options.xul

 <?xml version="1.0"?>
 
 <!-- This Source Code Form is subject to the terms of the Mozilla Public
    - License, v. 2.0. If a copy of the MPL was not distributed with this file,
    - You can obtain one at http://mozilla.org/MPL/2.0/.  -->
 
 <?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
 <?xml-stylesheet href="chrome://url-fixer/skin/options.css" type="text/css"?>
 <!DOCTYPE prefwindow SYSTEM "chrome://url-fixer/locale/options.dtd">
 <dialog
@@ skipping 23 matching lines @@
             <listcols>
               <listcol flex="1" />
             </listcols>
           </listbox>
           <hbox>
             <button flex="1" label="&urlfixer.options.removeButtonLabel;" onclick="removeRule(this,'whitelist');" disabled="true" id="whitelist_remove-button" _list="whitelist" />
           </hbox>
         </tabpanel>
         <tabpanel orient="vertical">
           <hbox>
-            <textbox id="find" flex="1" oninput="onFindChange();" onkeypress="if (event.keyCode == 13) { addRule();event.preventDefault(); }" />
-            <textbox id="replace" flex="1" onkeypress="if (event.keyCode == 13) { addRule();event.preventDefault(); }" />
+            <textbox id="find" flex="1" oninput="onFindChange();" onkeypress="if (event.keyCode == event.DOM_VK_RETURN) { addRule();event.preventDefault(); }" />
+            <textbox id="replace" flex="1" onkeypress="if (event.keyCode == event.DOM_VK_RETURN) { addRule();event.preventDefault(); }" />
           </hbox>
           <hbox>
             <button flex="1" label="&urlfixer.options.addButtonLabel;" oncommand="addRule();" id="add-button" disabled="true" />
           </hbox>
           <description id="custom_corrections-explanation">&urlfixer.options.regularExpressionExplanation;</description>
           <listbox id="custom_corrections" flex="1" seltype="multiple" onselect="onItemSelected(this);" _removeButton="custom_corrections_remove-button" _emptyLabel="&urlfixer.options.findAndReplaceEmptyLabel;">
             <listhead>
               <listheader label="&urlfixer.options.findLabel;"/>
               <listheader label="&urlfixer.options.replaceLabel;"/>
             </listhead>
             <listcols>
               <listcol flex="1" />
               <listcol flex="1" />
             </listcols>
           </listbox>
           <hbox>
             <button flex="1" label="&urlfixer.options.removeButtonLabel;" onclick="removeRule(this,'custom_replace');" disabled="true" id="custom_corrections_remove-button" _list="custom_corrections" />
           </hbox>
         </tabpanel>
       </tabpanels>
     </tabbox>
   </groupbox>
 </dialog>