1. Make the text way too small (under 10px)
2. Make everything a really bright color
3. Make everything a really dark color
4. Have an awful color scheme
5. Don’t optimize the images
6. Add flash animations everywhere
7. Add background music
8. Don’t make anchor tags look different from regular text
9. Make it all aligned in a weird way
10. Make the main navigation unfindable
11. Don’t separate any sections from each other
12. Make all of the pages look totally different from each other
13. Have text everywhere
14. Don’t put in any white space
15. Don’t put in an obvious navigation bar
16. Keep out a search form
17. Don’t give us any indication of where we are on the site
18. If you have tabs, don’t make them act like so
19. Make a totally bizarre layout
20. Don’t let us re-size the text
21. Let large images overflow their container and mess up the entire design
22. Don’t have a place to put the website logo
23. Have background images that really stand out
24. Use drop-down lists for navigation
25. Don’t test it out in different browsers
26. Use tables to lay out your design
27. Use multiple colors for the same type of object
28. Don’t make it obvious what we can click on
29. Don’t make headers stand out even just a little bit
30. Make it really complicated
31. Make it too wide (unless it’s a liquid layout)
32. Make it too skinny (unless it’s a liquid layout)
33. Mess around with the cursor’s appearance
34. Use CSS that isn’t compatible with most browsers without any alternates
35. Make it take a long time to load, even on fast internet connections
36. Put important stuff below the fold
37. Don’t make it accessible
38. Don’t add hover effects to links
39. Have a bunch of fixed images/sections
40. Have images that aren’t relevant to anything
41. Over-complicate any aspect
42. Over-simplify any aspect
43. Make it for a crazy font that nobody has
44. Use repeating patterns that are commonly used
45. Make it boring
46. Use really thick borders
47. Don’t add in common sections like a header or footer
48. Keep out any personality
49. Make it unbalanced
50. Don’t be creative

Though breaking one or two of these rules won’t really affect your design’s appeal, more faults will make it really easy to hate. Of course, the most creative designs break almost all of these rules