set AutoComplete off

To turn off the AutoComplete for the controls

In a page consider there is a "Email" textbox.
while entering the value in that textbox, you can see the previous values entered in that textbox.

how to avoid this?

It can be avoid by two ways

set "AutoComplete" to "off" to that form as below

<form id="form1" runat="server" autocomplete="off">
---
---
---
--
</form>

or you can also set for the particular control in a form

<form id="form1" runat="server">
---
<asp:TextBox id="txtEmail" runat="server" Autocomplete="off" ></asp:TextBox>
---
--
</form>