Why does Intenet Explorer see web sites so differently?

During construction of this site, I have viewed it on Firefox on both Mac and Windows, and Safari on the Mac, and it looks great! For some reason, I just fired up Windows to check it out on Internet Explorer…….

The last thing I expected was to see this:

Webernets screen grab in internet explorerWhy is it that the dominant web browser interprets web site code differently to every other browser? Who’s right and who’s wrong?

If you are viewing this site with IE, I apologise, and will try to sort this out soon.