POpUp Window

<script type="text/javascript">

function OpenPopup() {

    window.open("popup.aspx","List","scrollbars=no,resizable=no,width=400,height=280");

    return false;

}

</script>

for link button :

OnClientClick="window.open('http://localhost/inventory/warehouse Stock/viewstocks.aspx',  'popup' ,'height=955,width=910,top=150,left=150,status=no,toolbar=no,menubar=no,location=no,scrollbars=no,resizable=no,copyhistory=false');"

http://www.velocityreviews.com/forums/t294803-calling-pop-up-window.html 
http://www.eggheadcafe.com/community/aspnet/7/10066984/aspnet-20-menu-control-opening-a-popup-window-withouth-menubar-etc.aspx
http://www.eggheadcafe.com/software/aspnet/35564887/opening-another-window.aspx


http://www.astahost.com/info.php/Create-Popup-Window-Javascript_t169.html

http://www.eggheadcafe.com/community/aspnet/7/10066984/aspnet-20-menu-control-opening-a-popup-window-withouth-menubar-etc.aspx

Using Ajax ModelPoupExtender:

====================

1) Assign a BehaviourID to the ModalPopupExtender using the BehaviourID attribute.

BehaviorID ="ModalBehaviour"

2) Use the $find method to get a handle to the Modal Popup Behaviour .

$find ("ModalBehaviour").

3) Call your hide and show methods on the acquired handle.

4) The Javascript would look like this.

<script language="javascript"> 

function ShowModalPopup() 
{
  $find("ModalBehaviour").show(); 
}

function HideModalPopup() 
{
 $find("ModalBehaviour").hide(); 
}

</script> 

http://blogs.msdn.com/b/phaniraj/archive/2007/02/20/show-and-hide-modalpopupextender-from-javascript.aspx