I've udpated the GL API and GLSL reference pages to Docbook 5 source and HTML5 output, so we can join the 2010s. They are now using MathJax for rendering equations on browsers that don't support MathML (e.g. everything except Firefox, basically). There's an improved (hopefully) sidebar navigation interface and some CSS changes to be more similar to the OpenCL reference pages. I might tweak the CSS a bit as the font sizes are larger than the old pages.
Because many people probably arrive at the man pages via search engine links, and because IE8 and earlier browsers don't deal well with HTML5, the old pages are now redirection links which point to the current index page but also allow escaping to cached copies of the XHTML Transitional output. Eventually these will be purged (I think IE <= 8 users are less than 10% of opengl.org site visits these days). Hopefully the search engines will start linking to the HTML5 pages soon, but that's outside our control.
If you have problems or other feedback, please report it here. Assuming no immediate issues crop up, I'll be repeating this exercise for the OpenGL ES reference pages in a day or so. The build instructions on the Wiki are now way out of date and will also be updated soon (quick version: you need the latest docbook-xsl-ns 1.78.1 stylesheets installed).
If you're using the Docbook sources and don't want to migrate to Docbook 5 yet, the old sources are still available in docbook4/ subdirectories in Subversion, but they will not be updated going forward.