And thankfully, you can avoid people who would hire them by having reasonable market rates.
HTML/CSS, $20-30 is a fair rate.
For PHP/MySQL, it can easily go up to 40-60.
How long have you been doing it professionally? I started at 15, then each year went up by 5 or 10, until I found a good market to work in and jumped from 60 to 100 for freelance. (I also don't particularly want a lot of freelance work, only projects I really want to do, so $100/hr is a good way to weed out projects.)
Well I have been doing this sort of work since I was about 16, between 16 and 17 I mostly did just basic HTML and CSS, then when I was about 17 I began PHP, MySQL, and a lot of javascript/jQuery. Since then I have done a lot of work with javascript/jQuery as I have been doing a great amount of work with ajax content loaded websites, the real source of my knowledge has been my social networking website that I started working on when I was about 17, which is the main source of my current skill level (which I believe to be quite high given my age and relatively short period of time doing this (I am 19, well just about 20 now)) I have done a few professional websites, and I have done a bit more freelance.