FireLess is a Firebug extension that makes Firebug display the Less filenames and line numbers of LessPHP-generated CSS styles rather than those of the generated CSS. This is an adaptation of the Firesass extension developped by Nex3
First, install FireLess.
Second, enable LessPHP's debug_info option like the example below :
$lc = new lessc();
$lc->debug_info = true;
FireLess requires LessPHP.
FireLess should work with all versions of Firefox after and including 3.0, and all FireBug versions 1.4 and 1.5. It might work with FireBug 1.6 (which is in development at time of writing), but that's not guaranteed.
FireLess currently requires the development version of Less, available from GitHub.