why does my Safari screen "grey out"?

Need more information. When I open Safari, there's nothing on the page until I enter a web address. Under what circumstances is your Safari page greyed out and have you been able to enter any web addresses to get to a site?

Try clearing Safari's cache : Settings > Safari > Clear Cache (and Clear History)

If that doesn't work then try closing Safari completely and then re-open it : from the home screen (i.e. not with Safari 'open' on-screen) double-click the home button to bring up the taskbar, then press and hold any of the apps on the taskbar for a couple of seconds or so until they start shaking, then press the '-' in the top left of the Safari app to close it, and touch any part of the screen above the taskbar so as to stop the shaking and close the taskbar.

A third option is a reset : press and hold both the sleep and home buttons for about 10 to 15 seconds (ignore the red slider), after which the Apple logo should appear - you won't lose any content, it's the iPad equivalent of a reboot.

Kings suggestions above are the right suggestions. Try them and report back......