What does *DUW* mean?

I've been putting off asking this forever so I don't sound like an idiot. I can't wait any longer though. What does it stand for?

Dial up warning...aka lots of pictures lol :D

Dial Up warning. In other words, if you have dial up Internet, it's going to take a LONG time to download all of the pics in the thread!

Thank You So Much! I'm old as hell, but this is my first forum. I definitely remember the dial up days!