Website has menu navigation / scroll problems in IE7.

Hey everyone. I’ve been trying to figure out the best way to ask questions here since I have several problems with my site. I’ll try and get to the point.

1.) I have a website hosted under a subdomain for testing purposes and have tried to validate the html and css using w3 validator and jigsaw. Depending on the URL I use – https://alt.beaufortmusicfestival.com (9 frameset type errors 4.01 Strict, CSS3 pass) OR https://www.beaufortmusicfestival.com/alt (passes HTML5 / fails CSS3 183 errors, mostly vendor extentions). Why do the links validate differently and which one should I be concerned with? How should I go about fixing them?

2.) The site seems to do OK under IE8(9?), Firefox (the late version I have??), Chrome, Safari and Opera, but IE7 (and probably lower) it fails with the menu navigation bar. It appears transparent and, the dropdowns display behind the featured content. I’m assuming this is a CSS or Doctype problem? Odd thing is though, under my “localhost/wordpress” install, under ie7, the menu “looks” OK but submenus still appear under the featured content.
There is also this weird scrolling problem where the page scrolls infinitely down. All of this thanks to Internet Explorer. I’m hoping some of these issues are interrelated. Does anyone have any idea as to what could be causing these problems? I have been working on this for several weeks testing and researching and finally just need to break and ask these questions. If I find a solution I will post it as I am sure other people have encountered similar issues. Thank you.

Other browser testing to follow, but I have been preoccupied with IE7 and lower since that seems to be my biggest obstacle currently.

Mystique Theme
Mystique-Child Theme with its own style.css using @import url for core.css
WordPress 3.4