Erratic background menu display!

This is a weird one, a problem that occurs at random:

When you first click onto our website, or while clicking around the menu on the website, you will for a split second see the a giant version of our Seahorse Logo in the background, with underneath it the text of all menu titles. This appears for a micro second and then disappears, being replaced with the proper website. This will occur at sometimes and not others, and happens so quickly that it’s impossible to capture a screenshot of it.

I can’t figure out why this is happening!! I’ve checked everything I can think of in the back end and can’t work it out! Any ideas??

Thankyou!
SDPS Admin

The page I need help with: [log in to see the link]