Hello @kartik,
You cannot check it from the server's side, but you can use javascript to detect it after the page has loaded. Compare top and self, if they're not identical, you are in a frame.
Additionally, some modern browsers respect the X-FRAME-OPTIONS header, that can have two values:
- DENY – prevents the page from being rendered if it is contained in a frame
- SAMEORIGIN – same as above, unless the page belongs to the same domain as the top-level frameset holder.
Users include Google's Picasa, that cannot be embedded in a frame.