Studies show that the majority of HR managers perform Internet searches prior to interviewing job candidates. If they link unprofessional content to your name, you may be crossed off of a list of interviewees.
However, studies also show that HR pros also take embarrassing online information with a large grain of salt. They know that context is important and that there may be a simple reason that your off-color video clips somehow gained a high Google ranking.
With that in mind, understand that an interviewer may question you directly about unprofessional online content. That person may just want to know if you understand how easily this kind of online information can affect your real-life opportunities. Express that you're concerned, too, and explain the steps you've taken to avoid future embarrassments.
Don't be surprised if an interviewer pushes even further. Some HR managers will go so far as to ask candidates to load their MySpace or Facebook profiles in the middle of an interview [source: Rosen]. If that's a chilling thought, be sure to scour your profiles and delete unbecoming information in advance.