I am a web developer with about 4 years of relevant work experience in my field. Recently, I went from making $30/hr working from home contracting for large companies to a full time job that only pays 40k/yr. The company I work for now is great, nice people, but a little behind the times.

I joined on with very little experience in SQL development but they put me in charge of querying the DB and making reports right away, so I had to go in head first and pick up that skill right away. Which is great, I'm happy I learned more of that, and really make good time when doing SQL now. However, I'm now doing most of their advanced SQL stuff.

The day I started, another employee who was running a MVC project based in Yii (which is the sole item that makes this company software) put in his two weeks. Two weeks later, I'm the only one who knows how to use, access, modify, or update this project. Its quite a large responsibility for an "entry level dev", no?

I am doing highly advanced jQuery for them to modernize their forms, webpages, amongst other things, a skill that I would bet on few Entry levels being able to do as well as me.

I may be wrong, but I feel that what I'm making now is not acceptable. We don't have reviews, ever, so I can't just wait for that.. so I was wondering.. do I sound justified in wanting to be paid more, and how can I make this happen?