We all agree that having someone wait 10, 20, 30 seconds for a website to load if that can be easily avoided is a bad idea, right?
Yet if you are using a big graphic as your backround, it might be what's happening: Depending on the background colour, the text may be unreadable while the background graphic is loading. The solution is to define both a background image, and a background colour that is similar to the colour of the image.
I've made a quick mock-up to demonstrate the effect.
