For the love of all things sane, stop using Comic Sans! It's like you're trying to communicate with us through a bad 90s chat room.
Use a clear and consistent font, like Arial or Times New Roman, not that fancy-pants Garamond stuff.
And for the sake of all our eyes, please, use high-contrast colors! You don't want to make us squint through our lattes.
Organize your code like a boss, or at least, like a mildly competent adult.
Use HTML for what it was meant for: to make sense, not to confuse.
And, of course, don't overdo it with CSS, or you'll end up like the CSS Titanic.