Microsoft provides the following sample code to be used in conjunction with a custom.js to disable Autocomplete in Sharepoint:
Create feature files that will inject content into the master page "AdditionalPageHead" section.
Create a new feature folder under SharePoint.
Create the Feature.xml and CustomSchema.xml files like below:
TEMPLATE\FEATURES\DelegateControl\feature.xml
===================
<?xml version="1.0" encoding="utf-8"?>
<Feature Id="<GUID>"
Title = "AUTOCOMPLETE Disable"
Description = "AUTOCOMPLETE Disable"
Creator = "creatorName"
Version = "1.0.0.0"
DefaultResourceFile=" "
Hidden ="TRUE"
Scope="WebApplication"
xmlns="http://schemas.microsoft.com/sharepoint/">
<ElementManifests>
<ElementManifest Location="CustomSchema.xml" />
</ElementManifests>
</Feature>
CustomSchema.xml
=====================
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
<Control Id="AdditionalPageHead"
Sequence="80"
ControlSrc="~/_controltemplates/custom/custom.ascx">
</Control>
</Elements>
2. Create a custom.ascx file and place it in the TEMPLATE\CONTROLTEMPLATES\custom\ directory of the 12 hive
Custom.ascx
====================
<%@ Control Language="C#" %>
<script type="text/javascript"
src="/_layouts/Custom/Custom.js" defer="true"></script>
3. Create your custom.js and place it in the Layouts/Custom/ directory of the 12 hive
Custom.js
====================
if (document.getElementsByTagName) {
var forms = document.getElementsByTagName("form");
for (var i=0; i<forms.length; i++) {
forms[i].autocomplete = "off";
}
}
----------------
Source: http://support.microsoft.com/kb/970782