Thanks to all for looking at my problem. It seems that the trouble is with my browser set up - which is a relief!
I run IE6 with XP home.
SKy....I cannot find any setting to enable/disable frames. I went to tools>advanced and reset to its default, but it made no difference.
dl65....I have cleared the temp internet files and also run Internet Sweeper, which clears other internet related files (including hidden), and refreshed, but still no joy. Thanks for pointing out that 'About us' doesn't link. It is in fact supposed to be a heading. I think I'll change its colour or font to make it stand out.