Please check out these two URLS :

First url, HTML 4.0
Second url, XHTML 1.0

When I open the first one in IE6, i get what i want, which is the 4 words take a certain percentage of the page.

When i open the second one in IE6, which is exactly the same except for the doctype which is this time set to XHTML 1.0 transitional, it doesn't work anymore, the 4 words are centered and it seems not to take into account percentages anymore.

When i open either of them in netscape 6 / opera 6, i get every time the same result (the bad one with no percentages).

I can't find out what's going on, the code is VERY simple using only divs and spans... Especially the fact it doesn't work anymore on IE when doctype set to xhtml upsets me since i was trying to move my html code to xhtml, so now if this makes everything not working anymore i'm not that sure i want that...
Both pages validate in w3c validator respectively as html 4.0 and xhtml 1.0.
By the way what does the "transitional" part of the doctype mean ?

Thanks for any help
Quentin