From MozillaZine Knowledge Base
Find As You Type (or Type Ahead Find as it was originally called) allows you to start finding text on the page immediately by simply typing the text you’re trying to find. After a set amount of time with no further keyboard input, Find As You Type can be deactivated. This preference determines that set amount of time.
Possible values and their effects
Valid values are positive integers, representing the number of milliseconds before FAYT is deactivated. The default value is 5000.
First checked in
2002-08-19 by Aaron Leventhal (checked in as a default feature rather than packaged as an extension)
Has an effect in