You need to learn a lot more than HTML (the basics in an evening) to be a marketable prospect. Do you want to be a designer,a coder or both?
To be a coder:
XHTML / CSS / Javascript / PHP / MySQL / XML / Flash (maybe)
And if you're not any good at design then you'll still need to be working with a designer:
Photoshop / Illustrator and also HTML / CSS (you need to know that what you're designing can be built)...
Not wanting to sound like a wet blanket but just be aware that this web design malarky isn't the cakewalk it might first appear.