Firebug loads automatically on a refresh

Question

I recently changed my wordpress theme on my website with Chrome.

And since then, each time I load my website, the firebug lite plugin appears for 1/2 a second and disappears. It does not do it on the first load for Safari, but appears again if I ask a refresh of the page on Safari.

http://www.lebeauparleur.com/

I mean, WTF?

Thanks in advance,

Alex