Selftests from others

There are many self tests to be found on the internet. The list below is only a handfull. I'll add more links. Enjoy!

HTML

http://www.echoecho.com/quiz.htm
HTML quiz
HTML revision quiz
HTML QUIZ Online Test
HTML Quiz
HTML practice test - HTML online test - HTML quiz test
W3Schools HTML Quiz
W3Schools HTML5 Quiz

CSS

http://www.echoecho.com/quiz.htm
W3Schools CSS Quiz

JavaScript

http://www.echoecho.com/quiz.htm
JavaScript Quiz Test
JavaScript Web Quiz
JavaScript Quizzes
JavaScript Basics Quiz
JavaScript Arrays Quiz
JavaScript Quiz: What does this function do?
Final Javascript Quiz
JavaScript Test Questions
Javascript Scope Quiz
Perfection Kills JavaScript quiz
W3Schools JavaScript Quiz

jQuery

W3Schools jQuery Quiz

Bootstrap

W3Schools Bootstrap Quiz

AngularJS

Top 25 Angular.js Interview Questions

XML

W3Schools XML Quiz

PHP

W3Schools PHP Quiz

Structured Query Language (SQL)

W3Schools SQL Quiz

Active Server Pages (ASP)

W3Schools ASP Quiz

Other resources

W3Schools Forum
Testdumps (free test exam questions)
Aiotestking (free test exam qustions, including discussions on them. Please note: some of the answers given are in dispute.)