Firebug Lite
Firebug is an extension for Firefox, but what happens when you need to test your pages in Internet Explorer, Opera, and Safari? If you are using console.log() to write to Firebug's console, you'll wind up with JavaScript errors in these other browsers, and that's no fun.
The solution is Firebug Lite, a JavaScript file you can insert into your pages to simulate the Firebug console in browsers that are not named "Firefox".
Installing Firebug Lite
First, download firebuglite.zip and unzip it into any directory on your web server. Then insert this line of code into any page that you want to contain Firebug:
<script language="javascript" type="text/javascript"
src="/path/to/firebug/firebug.js"></script>
If you don't care to simulate the Firebug console, but you want to prevent calls to console.log() from causing errors, then just change the file name in the snippet above to "firebugx.js", like so:
<script language="javascript" type="text/javascript"
src="/path/to/firebug/firebugx.js"></script>
If you don't want to install Firebug Lite, but you just want to avoid those annoying JavaScript errors, grab firebugx.js here and just copy and paste it into your code.
Using Firebug Lite
Firebug Lite won't intrude on your page until you open it yourself. Just hit the trusty F12 key to open the console - it will appear at the bottom of the page just like the real Firebug.
You'll soon get tired of hitting F12 after every time you reload the page. If you want the Firebug console to be open every time you load the page, just add debug="true" to the html element of your page, like so:
<html debug="true">
Using the Command Line
Firebug Lite also contains a command line, just like its big brother. You can use the same shortcut you use in Firebug to focus the command like, Ctrl+Shift+L (or ⌘+Shift+L on Mac).
Try it on This Page
Firebug Lite is embedded in this very page - hit F12 or Ctrl+Shift+L right now to try it.