I think there may be a very easy solution to this problem. However, I have tried my best and couldn't fix this.
If you go to my blog http://www.carbonxiv.com
you will see my sidebar shifted to the bottom right corner... when should be beside the content instead.
I have no clue why this happened since I did not change anything on the server. All I did last night was reformatted my computer and then installed the FTP again... I checked the index.php, sidebar.php and CSS files and couldn't figure out what happened.