From MozillaZine Knowledge Base
This preference controls whether HTML links are underlined when the page does not define whether they should be.
Possible values and their effects
Links are underlined by default. (Default)
Links are not underlined by default.
Mozilla Suite and SeaMonkey
Edit -> Preferences -> Appearance -> Colors -> Underline Links
Tools -> Options -> General -> Content -> Colors... -> Underline Links
First checked in
Has an effect in