DropdownList not appearing while using Modalpopup IE6

I add this problem, i found few interesting blogs for this

http://vincexu.blogspot.com/2009/05/ajaxcontroltoolkit-combobox-not.html

http://forums.asp.net/t/1105102.aspx#2449650

FireAtlas – Firebug for ASP.NET

FireAtlas is a Firebug extension dedicated to ASP.NET AJAX. It enables tracing of PageRequestManager events, Partial Updates and WebService calls.
It lists all ASP.NET Ajax components instantiated in a page.

FireAtlas will provide you with useful services when developing ASP.NET AJAX web sites:
* PageRequestManager events tracing
* WebService calls tracing and inspection
* Partial Update inspection within Firebug Net Panel
* ASP.NET Components listing

This add-on can be downloaded here.

Here are the extensions available for Firebug.