Not all css is applied

This issue has me baffled...

I've created a custom front page using my good old copy of dreamweaver and applied it through Front Page Module. (Full mode - full html - html page in the data field with correct link to the css).

A preview through Dreamweaver (firefow, chrome and IE) shows every element where it should be, however, when I view the page on my Drupal site, not all the css is applied.

Anything 'style-related' (backgrounds, font, colors,...) comes through fine, but when it comes to positioning; the page seems to be possessed.

For instance; I have a wrapper element to keep the divs inside them in check when the screen is resized.

This is the original code for the wrapper (which also shows up when I click the wrapper div class using Firebug):

.wrapper {
    height: 620px;
    left: 50px;
    margin-right: 50px;
    min-width: 1260px;
    position: relative;
    text-align: center;
    top: 50px;
}

But when I simply hover over the wrapper using Firebug, this is the only css that's actually applied:

.wrapper {
    text-align: center;
}

Similar things happen with the divs inside the wrapper. As a result, the last one jumps to the next line (even when the screen is more than large enough to accommodate him) and the whole layout is off. It's possible to tweak by adding for instance top:-612px; but that doesn't solve the other positioning issues (the min-width for instance) and is plain ugly besides.

So, in other words; he knows about the css but just plainly ignores it.

According to FireBug, the only other css applied to this particular div is what's in the body, which contains nothing that can interfere. I cleared my caches, so that's not where the problem lies.

Does anybody have a clue? Thanks in advance!