That depends. Do you want to be just a web designer, or also a developer? Or, do you want to be development-focused?
All three are their own complete careers. Trying to do it all tends to result in none of it being done very well. With both development ones, use of things like LESS and SAAS are also becoming a big deal.
A few sites you can use to get started include Codecademy.com, TeamTreeHouse.com, HTMLDog.com, and W3Schools.com.
college, personal experience