browser compatibility

Hello, i have an issue with Flexx Dark theme on my site. It shows up perfectly in IE 9 but if i go to view it in chrome or FF there is a huge white space at the top of my page and the site appears half way down. I have been looking at how to get my blog to be compatible with other browsers but nothing so far has seemed to work.
The site this is happening on is: https://www.stretch-n-grow.co.uk.

When i right click at the top it looks like there is a flash movie embedded there but i honestly don’t know why and what to do. Any help is fully appreciated.

Thanks in advance.