If you read no other free tutorial this summer then this is the one you need to work through. Do not stop for that morning expresso, go directly to the 21 part series on HTML5 CSS:
HTML5 & CSS3 Fundamentals: Development for Absolute Beginners
If you are like me and are used to working with C#, VB, C++ then HTML 5 is interesting but confusing. So seriously take a look at the well written and edited tutorial at the link I gave you.
Do it now.