And also, what is the job pool like around you? Certain companies just don't pay as much as others.
If you want to continue web dev, learn the backend. Take some time, and write a small webapp in Django, Rails, Play Framework, Node, and anything else that sparks your fancy (and learn their accompanying languages).
Also, one other thing that will get you paid really quickly is databases. Learn your RBDMS theory, optimizations, normalization, etc. And learn about some noSQL databases, and you will qualify for a whole different class of jobs, which will be higher paying, for sure. Much less people are knowledgeable about databases.
These days, the easiest and quickest way to get a rise in paygrade is to switch jobs and renegotiate.
[EDIT] - philliphodgen's answer is possibly more right than this one. A practical application: go look on job sites like glass door, and see how much money is getting paid on average for which job descriptions, then get those skills.