I'm currently working on a new website, but I'm having problems positioning the elements on my page - When I make the browser window smaller or view the page in a low resolution, the "Sign up" box moves and covers the rest of the page. I'd like to know how to adjust my site so that when I resize the window or view the page in a low resolution, the elements stay where they should. Perhaps I've made some sort of fundamental error.. I'm rather new to web design. Here's the page and the CSS:
I'd really appreciate some help.