Popular browsers, such as Internet Explorer and Firefox support something called Auto-Complete. You've seen this many times. You go to a online form and as you start to type in fields you get a drop-down showing values you've typed in that field before. This feature can be turned off, but it really is a useful feature and can save you a lot of typing when entering redundant values.
<form id="Form1" method="post" runat="server" autocomplete="off">
<asp:TextBox Runat="server" ID="Textbox1" autocomplete="off"><!--asp:TextBox>or at runtime: