And if I get this TN visa, if I switch jobs, I dont need to renew it right away or anything right?
It's up to the border officer to decide whether you meet the critera or not. They're not experts in any particular field, so generally, they look to make sure that all the right keywords are hit in the job application and your qualifications.
Contacting USCIS will generally only get you generic advice. An immigration lawyer, while not necessary to do the paperwork (it's pretty easy) should be able to give you a reasonable opinion as to whether you'd be successful or not. They're the only people that deal with this often enough to have a feel for when an application might be successful or not.
Do some google searching on "TN visa" and "web developer", there are lots of stories out there that should give you a feel for what's involved.