How do I locate military records of an ancestor that served in the U.S. Army, 11th Airborne Division? I need guidance to a reputable site.
Am I entitled to search records of an ancestor?

I am currently researching a family member's role in WWII. I would rec that you start by submitting a request with the US Govt. at www.vetrecs.gov and follow their instructions. It may take a while to get any info back, one man waited 4 months before he got anything back, but it's official and from the govt's records so it's worth the wait.
Good luck. I would also tell you that I've discovered a lot just by going to www.google.com and ask.com and researching sites there. I've learned a good bit about my grandfather's battalion just by searching using those sites.

You may have discovered this by now, but for anyone with similar questions:

Reynolds is correct, but there's more...

All of these records are kept in St. Louis, and the personnel center website gives you everything you need to know:

http://www.archives.gov/st-louis/military-personnel/.

Before you get too excited though, be aware of the catastrophic 1973 fire that destroyed all the files of as many as 18 million veterans:

http://www.archives.gov/st-louis/military-personnel/fire-1973.html

Good luck! And don't forget that there are other ways to investigate, as Reynolds also suggests...