He's right - it looks like its sold out.
You can't book from the Hotel directly anyway. Instead you have to book online at this url :
http://internext-expo.com/hotel.html. Click BOOK and you are taken to Starwoodmeeting.com who are handing the actual bookings.
When I try it I get
The Westin Diplomat Resort & Spa, Hollywood, Florida - 'FOR ONE OR MORE OF THE DATES YOU SELECTED, ROOMS ARE TEMPORARILY UNAVAILABLE FOR THIS BLOCK .PLEASE CONTACT
[email protected] OR 954-602-8700 TO INQUIRE ABOUT YOUR ROOM RESERVATIONS
No rooms are available for the criteria provided. Please try your search again
Cool and Congrats to Internext!
or call 1-888-627-9057