HTML and CSS Reference
*Safari's Develop menu must first be switched on under Preferences ⇒ Advanced.
Prior to version 10, Firefox didn't come with built-in developer tools. I highly recommend an add-on called Firebug
both in the absence of tools prior to version 10 and in place of the built-in tools available from version 10 onward.
Firebug has more features than the built-in tools and is more consistent with those available in other browsers.
To install Firebug, in Firefox, click Tools ⇒ Add-Ons to open the Add-Ons Manager. Search for Firebug and then
click the Install button. After it is downloaded, click Restart Now (or close and reopen Firefox manually) to complete