XHTML and CSS
XHTML and CSS standards on the Web Design and Applications section of w3.org
XHTML tutorial of the W3C Consortium
XHTML 2.0 tutorial of the W3C Consortium
Tutoriels XHTML et CSS sur le site des tuteurs de l'ENS
Multilingual CSS tutorial of w3.org
PHP
The "official" php.net website
Club des développeurs Web PHP sur developpez.com
Latex and related
CTAN , the Comprehensice TeX Archive Network
bibtex2html : a small PHP script which converts a BibTeX file into Html code