>That is a no-no. You should never address a letter unless you know at least the name or the gender of the person. Real life forces us to though, so commonly accepted salutations are:
>
>Dear Sir or Madam:
>Dear Madam or Sir:
>To Whom It May Concern:
>

I'm usually using the first form. In most positions advertised on the Web you would not get the name of the person. But sometimes if you know the name you may not know the gender. So, would it be OK to write:

Dear Tracy Holzer,

I am writing in regard to the ... position which I found advertised at ... web site.