autocomplete off at master page

 I want to disable the Autocomplete altogether from the entire site.
So I was trying to do that in master page. 
But when I use <form id="form1" runat="server" AUTOCOMPLETE="off">
It gives warning that "Attribute 'AUTOCOMPLETE' is not a valid attribute of element 'form'."

Am I doing it at a wrong place??
 
Thanks!

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