Need an idea for the best way to check status of a webpage database

Here's my dilemma, and I'll be happy to pay for good suggestions: I have a toolbar application that people download and use while surfing the web. I also have a database that contains a little data about 100,000 or so webpages. Whenever someone visits a page that I have data about, I would like my toolbar to flash a green light or something. But don't worry about how that works. Here's my problem... What's the most efficient way of knowing if I have data about a certain page without pinging my database every single time a person visits a webpage? If the app hits my database every time a user visits a webpage, and I have 150,000 users, I'm going to be getting 15 million database queries a day, and that's just too much for my poor little server. There's not enough space in a cookie to store the pages I have information about. I could automatically download a file to the user's harddrive containing the list of webpages I have data about, and the app could just check that, but that would be a pretty big file too. Maybe there is no easy solution. But I thought I'd post this and let you RAC geniuses think about it. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Exclusive and complete copyrights to all work purchased. (No GPL, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site). ## Platform idea - text file okay.