I've been working as a Web Developer for the last 5 years ... but as others have mentioned above, yo need to decide whether it's designing or development you want to get into ...
You'll need to know HTML and css for both, but developing requires a knowledge of some server side scripting code, such as Asp.net, Php, C# etc ...
I'm not that creative so I don't really do any design work ... My job is to get the pages to work once the designer has made them look nice .. LoL
HTML 5 is definitely something to look at though ... I think a lot more companies will want to move their existing sites to HTML 5 for mobile solutions..