In Rochester, New York (medium size city in the Upstate area – far from NYC), I find you can do contract work as a front-end web developer between $36 and $43 an hour. Most projects last anywhere between one to 12 months. In the same area, you can freelance for $75/hour. And when you freelance, you can assume that every billable hour takes another hour to get and manage it (unbillable), so your effective rate is right back to the contract range: $37.50/hour.
Depends on experience. Mid-career level pays a whole lot more than entry-level (less than 3 years of experience). It also varies heavily from location to location. Here in Florida they pay only a third of what say, New York, is willing to pay.