I want to add IFrame to my Silverlight web site. and into that iframe i want to add aspx page. is that possible? (aspx page in silverlight.)
It's posible in your HTML where you call the Silverlight xap file, but not inside Silverlight itself
Yes you can add what ever asp / html elements to the web page where your silverlight application is running.
For example modify the ProjectNameTestPage.aspx in your web project.
Actually it is possible to have HTML content nested within the Silverlight, Telerik for example has a control called "HtmlWindow" or "RadWindow" which does just this. Either you could subscribe to their control set or try and find out how they did it.
I have used Telerik's control multiple times in an MEF Silverlight application where different web applications (SSRS for example) are contained with the MEF plugins.