This is just part and parcel with the territory and is the risk you take as an independent contractor or freelancer. It's generally not acceptable (and certainl

This is just part and parcel with the territory and is the risk you take as an independent contractor or freelancer. It's generally not acceptable (and certainly will not make happy clients) to quote one price and then charge another, you just have to get better at estimating both time and cost. The two biggest parts of creating an accurate estimate are understanding and defining the scope of the job and, if working with an existing system, understanding that system the best that you can. If you and your client determine that you will build a simple, 5 page, HTML/CSS website for X dollars in X weeks, then your client decides that he actually needs 15 pages and it should be a wordpress site, it's time to renegotiate your price and timeline. However, if you just get stuck on something you had already agreed to deliver, there's not a whole lot you can do. You can always try to get more money, etc., but there's no gurantees. And you should know this happens all the time - to freelancers and big corporations bidding on contracts. Live and learn.