Proper grammar and spelling. Concise description of what the organization does and how the job fits into the organization's activities. For software positions the technical mix should make sense.

Do they have a realistic job description? Or do they describe things in a way that would make even Superman wonder if he might be qualified?

on that note, the job description should also be an accurate reflection of what to expect during the interview, which should be an accurate description of the position responsibilities (and not a catch-all wish list)