The current beta version of Firebug doesn't appear to install on Firefox 3 on CentOS 5.2, apparently because it's reporting itself as 3.0b5 rather 3.0. I tweaked the minVersion requirement in the xpi to 3.0b5 and it seems to be working fine for me now. In case anyone else is interested in testing it, my tweaked version is available here: http://www.openfusion.com.au/labs/dist/firebug-1.2.0b4-fx.xpi If it turns out to be stable we might be able to convince the firebug team to relax the minVersion requirement for us CentOS users. Cheers, Gavin