Frame sets

I have set a frame set with a mainframe of 428, the pages which I want to sit in this frameset are in a table theat is exacty 428 high and the page porerties are all set to 0 however when I veiw the frameset I am missing some of the mainframe page why is this ? Take a look at the site it might make this question clearer www.richardpettit.co.uk