Yes, you read that right :-)
Saw it just now in their email newsletter.
The discount is on all stuff at the Pragmatic Bookshelf, only on Friday, that is: from "00:01PST to 23:59PST on Friday, November 28th. (PST is 8 hours behind GMT)", according to the newsletter.
Here's the direct link for more info on the scheme.
They're offering "25% off everything in the store—books, PDFs, and screencasts (the only exception is The Pragmatic Programmer book itself".
The reason they are doing it is to celebrate 5 years of their publishing company's existence.
(*) Incidentally, that book "The Pragmatic Programmer" is really very good. If you're interested in improving your general software development skills, it's very useful. I've read it.
Vasudev Ram - Dancing Bison Enterprises.