> I grabbed a web site and every time I click on the
> link I am getting an error message
> Line:46 
> Char: 5 
> Error: 'top.hidden' is null or not an object
> Code: 0
> ...
> 
> What coud be the reason and how to eliminate the
> problem?

It's an error caused by some javascript that is looking for a certain frame. 
Either the frameset wasn't mirrored or the page is being viewed outside of
that frameset.

(...stupid javascript coders... grumble....)