1. What is HTML?
  2. What are the different versions of HTML?
  3. What about XHTML?
  4. Is HTML case-sensitive?
  5. What does the DOCTYPE declaration do?
  6. What is a DTD?
  7. What is the difference between Strict, Transitional and Frameset DTDs?
  8. Which DOCTYPE should I use?
  9. Why should I validate my markup?
  10. Why does HTML allow sloppy coding?
  11. Why does the validator complain about my <embed> tag?
  12. What does character encoding (charset) mean?
  13. What is a BOM?
  14. What encoding should I declare?
  15. How do I insert characters outside the encoding range?
  16. Why do I need to write &amp; instead of just &?
  17. How should heading elements be used?
  18. What are block-level and inline elements?
  19. Can I make an inline element block-level with CSS?
  20. Why are external CSS and JavaScript files a good idea?
  21. Should I use p or br?
  22. What does “semantic” mean?
  23. Should I replace b and i with strong and em?
  24. Why are layout tables considered harmful?
  25. Should I use divs instead of layout tables?
  26. Are tables deprecated?
  27. What is the correct use of the address element type?
  28. What is the correct use of the dfn element type?
  29. What is the correct use of the var element type?
  30. Should I use quotation marks within or around a q element?
  31. What is the difference between abbr and acronym?
  32. Why is <feature X> deprecated</feature>?
  33. Must I have an alt attribute for every image?
  34. What is the difference between class and id?
  35. Why doesn’t id="123" work?
  36. Why doesn’t <a href=My Cool Page.html> work?
  37. How can I include an HTML page in another HTML page?
Do you know the answers?

Tommy Olsson has written an excellent article for SitePoint entitled “Bulletproof HTML: 37 Steps to Perfect Markup.” The article’s title is a bit misleading as it’s not actually outlining any process or steps to being a better designer, as it is answering some common questions regarding HTML. Olsson’s insight is invaluable for those new to HTML or those of us that thought we knew the answers to a few of the questions he poses.