IP Ports and Internetsecurity. Information about a specific port, just add the portnummer, e.g. for Port 113: «http://www.gsc.com/port_113.htm».
Network SuperPage.
http://www.eee.bham.ac.uk/woolleysi/video_on_demand/contents.htm
xDSL Docs.
http://www.nextep.com.au/whitepapers.htm
xDSL Tutorials.
http://www.etsi.org/technicalactiv/xdsl/xdsl_tutorial.htm
Connector pinouts.
RJ45 wiring.
http://yoda.uvi.edu/InfoTech/rj-45.htm
File Format Extensions.
http://www.e-tech.ca/008-FileFormats-a.asp
File Format Specifications.
Ethernet Cable Tutorial.
http://www.lanshack.com/cat5e-tutorial.asp
Tester for robots.txt (engl).
http://www.searchengineworld.com/cgi-bin/robotcheck.cgi
Information covering Search Engines
http://www.smart-it-consulting.com/
The ultimate HTML, CSS, JavaScript reference (German)
The ultimate PHP reference (German)
The ultimate mySQL reference