I want a mechanism by which after accessing a page for 3 attempts the page should become disabled or back button is disabled on browser in my ASP.NET application.
Also my text boxes r displaying the last few values entered which i do not want. For eg: in security-text textbox it displays the values entered in last few attempts.

Also I want to track the IP address. How can i do it?
Can anyone tell me.

For Disabling:
You can create an static variable and increment that variable when page loads and if count is 3 disable all the controls in the page.
For values entered:
   You can diable the viewstate
To get IP Address:
   It will be in the Request Header information.YOu can track IP address using that information

But the thing is that the user can use the Back buton of Browser and can continue which i donot want

You can avoid users use the back button by redirecting user to the same page.
This you can do with the javascript.Code is below
<script language="javascript">
  if(history.back)
    history.forward();
</script>

Santhi can u tell me the .NET equivalent to this code bcoz history is no command in .net

In .NET there is no command for this.U use that javascript..Add that in your .aspx file..