Turn off the "autocomplete" feature of the browserTag(s): Form
Modern browsers include a feature called AutoComplete that keeps track of information that you've recently typed, such as Web site addresses, information in forms, and search queries. As you type new information, AutoComplete tries to anticipate what you are typing and offers possible matches.
If you don't want the browser to remember previous typed data then you can set the attribute autocomplete to "off".
<form> <input type"text" name="username" autocomplete="off"> <form>
You can disable this functionality completely at the browser level, see IE, Firefox