I want to extend JFrame needed for my GUI program but i get this..

http://imageshack.us/photo/my-images/209/screenshot20111226at163.png/

how do i solve this?

When you have a serializable class you're supposed to define a serialVersionUID that ideentifies the version of the serialized form - if you change how it's serialized you're supposed to change the serialVersionUID.
It's a complete waste of time and a real annoyance. Either ignore it, or create a private static final long variable called serialVersionUID and give it an arbitrary value, eg 0, then forget it.