Help with site layout problem

Hi,
I run this Farsi site and yesterday, I posted a few articles and suddenly I noticed my sidebar is out of its place! It is using wordpress and I must say, I did not change any css or did anything with the theme...just did normal posting.
Would you kind people tell me how I can find out where the problem is in these cases?

I checked to see if there is any extra code in the text of the articles recently posted, but found nothing...pure text and few <a> and <img> html tags....
size of the pictures are also moderate as you can see...

I know you can't read the text, but where do you think I should look for the problem?

the site address is http://punez.nafice.com

I think you might have made some changes in the theme files. The order of the element seems to be incorrect for a two column layout.

Thanks!
I don't remember editing the theme in anyway!
But it was working fine early morning that same day...I am confused..

One thing is, if you know wordpress, the mess up is only on the main page (index.php) but it works in single page view (single.php)...any ideas?

Maybe you forgot to close a HTML tag when you posted your new post?

i thought so too...but I couldn't find anything bad...
anything else? anyone else had this problem?

There are some mark-up errors (http://validator.w3.org/check?uri=http%3A%2F%2Fpunez.nafice.com+&charset=%28detect+automatically%29&doctype=Inline&group=0).

and some css errors (http://jigsaw.w3.org/css-validator/validator?uri=http%3A%2F%2Fpunez.nafice.com+&profile=css21&usermedium=all&warning=1&lang=en).

Frank