change the URL to something more friendly

[eluser]mistress_shiira[/eluser]
hi guys!
i have a controller that loads a certain view file.
the URL seen on the browser is this:
http://localhost/CodeIgniter_1.5.3/index.php/Admin
that view file basically shows a log in page.i have a function in my controller that checks for validation.
in my view file i have this line
<form id="admin" method="post" action="validate">
where validate is the name of the function that checks for validation
after it has validated,it would go to another view called main.php
the url becomes this:http://localhost/CodeIgniter_1.5.3/index.php/Admin/validate
how will i be able to change the url so that what is reflected is the base url and the actual name of the page?