From MozillaZine Knowledge Base
This preference controls the amount of time in milliseconds to show "Downloads Complete" & "New mail" -style of alerts that appear in the bottom-right.
Possible values and their effects
Any positive integer. Thunderbird default: 3000 (3 seconds). All others default: 4000 (4 seconds).
First checked in
2002-03-22 by Scott MacGregor.
Has an effect in
- Netscape (all versions since 6.1)
- Mozilla Suite (all versions since 1.0)
- Firebird (all versions)
- Firefox (all versions)
- Sunbird (all versions)
- SeaMonkey (all versions)