Script Validation Of Html Select/option Tag?

I have a form and I have gotten all of my error checking to work except for this. I use an <select><option> list for a states dropdown. the 1st option is blank <option></option> I have not been able to successfully check for errors (no option selected) it either always gives and error using if(state==null), or never gives an error state=="" or " " this is the only dropdown on this form so I didnt notice the problem until I had gone through all the more difficult error checking, and somehow I cant get this one seemingly simple thing figured out