Gmail produces the following error/warning in firebug.

Eb is not defined

function Bb(a){if(a[sb]&&a[sb](daa)){var'ents)};f.x2b=c;f.B2b=b;f.y2b=a;return f}

I initially started seeing this while while on clients’ websites, but can now say it’s a gmail thing. So don’t stress.. 😉

This shows up because Gmail’s minified JavaScript uses short variable names like Eb, and Firebug picks up on references that don’t resolve in the current scope. If you have Gmail open in another tab, its scripts can bleed into the console output. It’s completely harmless and has zero impact on your own site’s functionality. You can safely filter it out in Firebug’s console settings or just ignore it entirely.