Teensy icons for bookmarks?

[ffutures]

Some web sites (e.g. Livejournal) have little icons that get added to the bookmark for the site (in Livejournal's case a little pencil). How easy is it to do that? Does it need complex code, or is it dead simple? And is there any reason not to do it?

Later: Thanks to everyone who commented - I'll give this a try.

Comments

[ramtops.livejournal.com]

Google on favicon - that'll tell you how it works.