Hm, definitely something wrong there. There is hardly anything on your page at this stage. Is that intentional? You should run your page through the validator, as there are quite a few errors that could be messing this up a bit. The code needs a lot of work in various ways. For example, all those <br> tags are out of place. You should be using margin/padding etc.
You are also using some new HTML5 elements (like <nav> that have no support in older browsers, so you need to help them out in some way, such as with the HTML5 shiv. Also, if you are going to use those elements, you should have an HTML5 doctype, rather than an old HTML4 transitional doctype.