Hai , An asp panel contains only 6 events. if they provide a visibilechanged event it may very useful for me. if it is in windows application ,how easy it is.I dont know why thy are not providing all these.This is same as in the case of gridView, button ,etc.

just think , I have an Iframe in an asp panel and two buttons. In first time it is invisible .Buttons named first and second respectively. Two another pages One.aspx,two.aspx. These two pages contains each text box. When you click on the First button . I want to set the Iframe src="One.aspx" and display "first" in the textbox on One.aspx. as same in the case , when user clicks Second button. How to do this ?