Firebug and firebug lite were amazing but to keep the record clear it was possible to debug client-side JavaScript (and other script types) using Visual Studio since very early on in IE. It was granted a major pain to setup properly for breakpoints and code highlighting but it was a full fledged debugger and IDE. I remember doing it often. I don’t remember if there was a debugger for IE for mac and early Safari. For me those where where “alert” and “document.write” were my only options.