Manage -> Pages get Fatal Error Please Help

I have over 140 pages in my Book Craze site. I am looking at the possibility of over 500 pages once the site is completely through with the chance of even more pages. When I go to Manage -> Pages I get the following information and the page doesn’t load completely.

Fatal error: Maximum execution time of 30 seconds exceeded in /home/*****/******/bc.tigerwhispers.com/man/wp-includes/functions.php on line 23

Can someone please, explain to me what is happening & what can I do to fix this. I really would like to edit some of the pages, but until I can see the entire page I can not edit the pages without going through the front pages, & I don’t want to do that. So please help.