Depends. If it's a new project, choose the oldest thing that's still widely supported. Often times, this will be something like straight Java or PHP. It's not t

Depends. If it's a new project, choose the oldest thing that's still widely supported. Often times, this will be something like straight Java or PHP. It's not trendy at all, but it will run under 99% of system configs out there. Also, be sure to document your work as much as possible and give that documentation to whomever you're turning your work over to. If you're taking over another project, make sure the client has docs before you take it on. Otherwise, there's a good chance that you won't be able to deliver what they want. Best to avoid those customers initially (if you can).