I tried that even. But when I view source, in the javascript function I see it the ID as tabcontainer where as the actual client ID of the control in view source is "someguid_tabcontainer" i think "someguid" is the guid of the sharepoint webpart. that's why I gave this.UniqueID + "_tabcontainer" and it worked...

I just wonder why tabcontainer.ClientID is not returning the clientID. Problem is resolved yet I am curious to know this. I am including this code in createchildcontrols event of the webpart control and. The control is being added to UpdatePanel and the UpdatePanel to the webpart...