Help!!
If you haven't used frames before, navigation inside them is a little different to what you might be used to. If you follow a link inside the frame and want to go back to the last page you were looking at, you can't just press the "Back" button. That just takes you back to the last page you were looking at before you entered the frames. To navigate back within the frames:

PC Right click inside the frame. A menu appears with the options "Back in frame" and "Forward in frame". Follow them wherever you want to go.
Mac Click and hold inside the frame. The same menu I mentioned in the PC bit appears. Follow the signs wherever you want to go.

So, right click or click and hold on this message now and follow the "Back in frame" thing back to the main index.