What version of Windows are you running Gav?  XP, Vista or Win7?  Also what version of browser are you running?

Can you just confirm its only in your web browser which everything is screwed up?

If its IE, go into TOOLS and make sure COMPATIBILITY VIEW does not have a check next to it.

Next, go into TOOLS and INTERNET OPTIONS.

Select FONTS.

Make sure the drop down box at the top has LATIN BASED selected (should be shown)

Make sure the window WEBPAGE FONT: has Time New Roman and PLAIN TEXT FONT: Courier New

If all the above is correct and same, then as a last ditched effort, go to TOOLS and INTERNET OPTIONS.  Select ADVANCED tab.

Down the bottom is a button RESET.  This will do a 'factory' reset on your IE options.  Worth a try.

Make sure for virus software is up to date and to a full scan.

If its happening all over windows (ie not just internet browsing) we'll go to plan B.

First up - thanks everyone.
 I cant stand computers but seem to spend a lot of time on them!

Marty J - i did all that you suggested..... when i restore factory settings i can see all the ticks changing in the boxes..... go to a web page and all good then it goes cranky again after about 5 secs.

Go back to restore factory settings, click restore and all the ticks change in boxes again.

I did this approx 3 times and now Ebay listing page looks good, but my Ebay page is all cranky.. still cant open up any pics on any listings.

Ran anti virus and all good and also all updated.

Odd thing is that most other web sites appear OK... just Ebay now.
Auspinball looks good so far