Navigating url with Webbrower control

Question

Hi,
  I have a grid and a webbrower control on a form. When I will click on any record in the grid, a function composes the url as per the user's session id and the url should be navigated in the webbrower control.

here is my code  --

string _url  = ComposeChatScriptPageUrl(_sessionId);
 
  //_url value i get here is  http://localhost/web/ChatScript.aspx?sid=4wil4355awmve4fk0p02aqeg

browersCntrl.Navigate(_url); 
browersCntrl.Refresh();

but it's not navigating the page, even after browersCntrl.Navigate(..) I can see browersCntrl.url is null (?)

I can view ' http://localhost/web/ChatScript.aspx?sid=4wil4355awmve4fk0p02aqeg' in a browser with proper data.

For a trial i tried --
chat_browersCntrl.Url =new Uri("http://www.google.co.in");

but still after executing this statement , chat_browersCntrl.Url is null (surprising !! )

Can anybody help me out.. it's urgent !!!!