headers in IE7 are misaligned

good day,

i have modified the F8 theme and used for this website: https://www.birdingphilippines.com/blog

it works well with firefox and IE6 (and i think IE8) but when i view it under IE7 the header is misaligned. The red box surrounding the navigation links are way up near the “rss feeds” and the navigation links (home, contact us, etc.) are overlapping with the main content.

Please help as I am completely a newbie and has very limited knowledge in CSS and HTML.

Many thanks!