Clients FAQ:
Title - Why is my client flashing?
Some downloadable clients can alert you when there are new entries on your friends page. This feature is only available for Paid and Permanent accounts. [and EAs?]
Methods of this alert vary, depending on the client, but common methods include a flashing icon, a popup dialog box, or a sound. When your client produces this notification, it means that there are new entries on your friends page.
If your client is alerting you to new updates to your friends page, and there are no new entries that you can see, there are several possible explanations. The protocol that tells the client that there are updates does not distinguish between various security levels; if someone on your friends list posts a private or protected entry that you are not able to see, your client will still notify you. Also, if you see a new entry by loading your friends page, the client may still alert you to this entry if it hasn't already.
For information on changing the settings for this alert, or for disabling it, please consult the documentation for the client you are using.
Further reading
* What is a downloadable client?
* How do I get a paid account?
Vaguely considered having it also a "How do I get notification of my friends' updates?", since we get that question in support every now and then; would probably cover (a) the complete lack of email notification, which is what people seem to tend to want, (b) checkfriends via client, and (c) RSS feeds or something like that? Meh. Would still go in Clients though, probably.
Thoughts? Suggestions? Rotten tomatoes? Pocky?