You shouldn't be using XHTML Transitional. Using a "loose" version of XHTML completely defeats the point. 
It looks pretty decent, actually, even in text-based browsers. One thing I'll take issue with:
Code:
<div class="newbox" onclick="window.location='http://jigsaw.w3.org/css-validator/validator?uri=http://www.pixelcode.co.uk/main.css'" onmouseover="miniButton('over','cssend','cssfront')" onmouseout="miniButton('out','cssend','cssfront')"><div style="clear:both"><div class="newbox2" id="cssfront">CSS</div>
You should make at least one of those elements a link, for non-JS browsers. This occurs all over your site. Turn Javascript off in your browser options then try to browse your site. It's almost impossible.
Also, you've fallen into that pit of making the alt text for a bullet image the same as the text beside it, meaning that in non-image browsers, it looks like this:
Code:
Home // Index
* Side Menu
* HomeHome
* Site MapSite Map
* XML RSSXML / RSS
* Link BackLink Back
* ContactContact
* TutorialsTutorials
* DownloadsDownloads
* Web DesignWeb Design
* ArticlesArticles
* About PixelcodeAbout
* LinksLinks
Pixelcode - Welcome
* Pixelcode
* PHPPHP
* PhotoshopPhotoshop
* CSSCSS
* JavascriptJavascript
* HTMLHTML
* XMLXML
* DreameaverDreamweaver
* FireworksFireworks
* FlashFlash
* ::Statistics::
* Current VersionCurrent Version: 3
When you already have appropriate descriptive text beside the image, you can have a blank alt, or some kind of text bullet such as the letter o or double chevrons (»).
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