different browsers different look

hey i'm really a beginner in writing codes, and i'm encountering problems with the alignment of the page in different browsers.

this is my website: http://testing-weiting.blogspot.com/

i get problems when using an older version of IE, the alignment screws up totally, but it works perfectly well for safari and mozilla.

this is a zoom out version of the webpage on the older version of IE.

http://i71.photobucket.com/albums/i158/xntitled/Untitled.jpg

You can try validator (http://validator.w3.org/) and CSS validator (http://jigsaw.w3.org/css-validator/).

hey, thkx for suggesting that, din knew that existed.

but i get this error:

URI : http://www.blogger.com/css/navbar/classic.css
23 #leftcontent Property _margin-top doesn't exist : 30px

after googling i found that its a mistake in blogger and there's no solution to it right? anw what effects does it have on my blog? i can't find it in my codes!

i'm getting this 2 errors:

118 p.post-footer em In (x)HTML+CSS, floated elements need to have a width declared. Only elements with an intrinsic width (html, img, input, textarea, select, or object) are not affected

171 .paging-control-container In (x)HTML+CSS, floated elements need to have a width declared. Only elements with an intrinsic width (html, img, input, textarea, select, or object) are not affected

what do i have to do? cos i can't seem to solve my problem yet..
pls help me!
thank you :)