website

I'm not sure I understand the question. Can you be more specific about what you're looking to do?

Are you looking to create some sort of function where the site's index page is randomly replaced with one of your 1500 other pages? 

Definitely need some sort of server-side coding to figure out how to call those pages dynamically as you wish.  Are you using a CMS now, or have you been maintaining 1500 pages on your own?  If the latter, I would recommend looking into a CMS depending on what your server supports.

1500 pages as menu items is crazy. You would need to classify and group pages down to about 5 menu items. The 5 menu items can then be used to drill down even further using sub-menu items and so forth.