Customizing SharePoint Portal Server 2003 (thx to @baz)
This article is a guide for developers customizing SharePoint Portal Server 2003 (SPS). Typical customizations include logo branding, applying updated color schemes, modifying navigation menus or adding a header/footer. Intermediate knowledge of SPS, HTML and CSS is required.
The same concepts outlined below generally apply to Windows SharePoint Services (WSS), however, there are a few differences. See the resources section at the end for more information about customizing WSS.