As a follow up to Matt's How to Hire a Good Web Developer article, I thought I would expand on the subject a little more and discuss common traits good web developers have.  These are things I've noticed in working with or talking to web developers at all skill levels -- from someone who still uses Front Page all the way to Google employees who maintain large-scale web applications.  So, when you're hiring your next web developer, reflect on these traits as you talk with applicants about their work history, philosophies, and their personal growth.

Good web developers...

1. Are always unsatisfied with their work
   I mean this in the best way possible.  Good web developers should always be "not 100% satisfied" with their level and quality of work.  They should always be saying to themselves, "I can do this better."  The resulting behavior is a never-ending cycle of learning how to develop websites that are better, faster, and easier to scale, which means good things for you, your business, and your web application.
   
2. Have improved their skill set lately
   I've seen far too many crappy web developers who learned how to design with tables in 2001 or learned Perl back in 2000, and have been developing like that ever since.  I'm not saying that someone can't get really, really good at Perl and make a career out of it, but good web developers are always reading up on new technology or languages to improve themselves (see #1).  If they're not versed in it, they should at least be able to tell you a few new things coming down the pipe in the web development sphere.  If you're curious, that's currently micro formats.
3. Don't promise everything
   I know what my limits are as a developer.  I know that if someone asks me to create a Flash app or write anything more with JavaScript than some basic things with the Prototype framework, I can't.  So when a client or boss comes to me and asks if I can do it, I tell them that's beyond my limits.  This skill set inadequacy helps to fuel the fire behind point #2 as well.
   
4. Think ahead
   Like a good business developer, a good web developer should always be thinking, "How well will this work and/or scale down the road?"  It's a key component to both writing good code as well as creating maintainable and scalable websites.  If you ask a web developer if they can do task X, and they say "Yes," the next words out of your mouth should be, "Tell me how X will scale."
   
5. Are as accurate as possible
   Web development is a precise field.  Leaving out one character of code can render an entire website useless.  Good web developers always focus on making sure they understand and deliver things as accurate as possible.  They should show they understand the project goals and deliverables.  They should ask a lot of clarifying questions about what they're being asked to do.  And, they also shouldn't be afraid to ask follow up questions later on to make sure they get things correct.
   

Of course, not every good web developer has all of these traits.  But, I'd be willing to bet that all have at least one of them.  They're just things that show the web developer is passionate about what they're doing and cares about you, your company, and the future.