Strange Scroll behavior

I have a page with a picture and some text on the right side of the picture. Below the Text and the Picture i have the Spreadshirt-Shop. When i am on top of the page, everything is alright, but as soon as i scroll down, the spreadshirt categoryfilter- and the sort-dropdow jumps to the right and also my articles jump 2 steps to the right. I can provide some pictures via e-mail.

http://wordpress.org/plugins/wp-spreadplugin/