Coding Effeciently
You need to understand how to read, edit and troubleshoot basic HTML. You should be able to pinpoint a bold or font or color or size issue in HTML without thinking. You should be able to substitute styles in CSS with ease. These are skills that are easy to learn and will serve you well in the long run.
Using Frameworks
Frameworks keep you from reinventing the wheel with every project and are easy for others to use if you are ultimately handing a website over to a client that will try to maintain it and make updates. WordPress is a popular option, but there are plenty of others out there to try.
Javascript
While you can code up your designs using just HTML and CSS, if you can also program using JavaScript, you’ll have a huge leg up against the competition. JavaScript allows you to take static elements on your site and make them interactive—think: Twitter feeds that update automatically, websites that look different when you’re logged in, image sliders, and more!