Netscape had a JavaScript debugger, IE had a debugger as well. What firebug did was pull the inspector, debugger, console, and everything together in a really nice dev experience. The goal posts were moved far back and the major browsers hurriedly released their “dev tools” to counter FireBug. Chrome being the first after, followed shortly by Safari (who already had an inspector). It would take MS another 6 years to do the same for IE8.