Right menu bar floating under posts area on last page.

Sorry but I don’t see anything wrong on your blog.

Hello.
You could not see what is wrong because I changed the number of posts per page settings (now is 9), because I didn’t want it to look bad for my readers and then the problem disappeared. After playing a bit with the layout and number of posts per page settings, I have noticed that the widget bar floats under the posts section of last page, only when there is only one post on that page. So my solution will be to periodically change my layout/number of post per page in such a way that I always get at least two posts on the last page. However, any permanent solution to my problem will me much appreciated.
Thanks.

OK, I saw it!
Indeed, if you have less than four posts on the last page the sidebar (#secondary) is going inside the main content (#primary). But if you have four posts or more, everything works normal.

It’s look like a closing tag is missing somewhere there. I think is about the .three-col-wrapper.