sidebar goes down

Hi all.
I use the default theme, and i can say that the only changes i make is that i changed some colors code in the css style file. Recently, the side bar goes almost in the bottom. I tried the following but nothing works :-
1) I edited my posts & resize the pictures.
2) I edited my posts & set the editor “off”.
3) I removed all the pictures from the sidebar.
4) I upgrade 2 the latest verison.
5) I deleted some files & reupload new ones.
I did almost everything that may solve the prob, but nothing works.
Thanks in advance