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With most of us (and savvy customers) basing validation on the 2.1 9W3c)schema I think you may asking for some tight trouser days with 41 errors on the home page .
Appreciating that many of the newer browsers can handle opacity ,shadow etc already there are still many that cannot.
Certainly with ie6 which I no longer support but lots still insist - you could foreseeable notice performance problems as it cannot even render the current schema never mind outside.
The Vista thing is groovy but to my eye clashes with the first "screeny" on the left perhaps for the home page picking something more complimentary from your portfolio may serve you better. Im not sure if you are using Images for your text on the nav tabs but they are quite blurry FF latest at 1280 x 1024 . A basic screen size change courtesy web developer tool bar ff latest choppered your view port in half at the infamous 800x 600.
Switching off styles similar to a crude panic degradation test did render a usable page

thanks for your thoughts! I'm actually validating my site against css3 - I know it's not 100% valid yet - because of the use of some css3 effects.
I considered the 800x600 issue when making the site, but I'm not too worried about that because of the thousands of visitors my site has had over the last year, only 39 have been at 800x600.