Float not being placed properly

[Wedvich]

I have absolutely no idea what went wrong here, all I know is that everything worked well, and then... well... then it didn't.

http://xpssource.net/

And the CSS

http://xpssource.net/stylesheet.css

Any help to be received? I'm not very confident at CSS so I'm having trouble coming up with a theroy of where this goes wrong.

Oh, right, almost forgot - to specify the problem: as you can see, there is a box to the right. This box is supposed to float on the right side next to the news posts and such. Instead, it gets pushed down below them. As I said, it worked perfectly, and then suddenly it just stopped working. As far as I know, I did not make any changes to that specific part of the CSS, so I can't see the relation.

So please, if someone with a higher amount of skill and understanding of CSS than me would like to help me crack this nut, I'd appreciate it.

[Kravvitz]

Put the #rightbox before the other elements in #layout.

You should use a complete doctype (one that includes a URL).
http://hsivonen.iki.fi/doctype/
http://www.alistapart.com/articles/doctype/
http://www.juicystudio.com/choosing-doctype/
http://www.w3.org/QA/2002/04/valid-dtd-list.html

http://www.tjkdesign.com/articles/boxmodel.asp
Difference between box models, doctype switching, etc. (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnie60/html/cssenhancements.asp)
The Box Model Problem (http://www.communitymx.com/content/article.cfm?cid=E0989953B6F20B41)