You can simply Google 'Firebug' and you will have instant access to download Firebug.
To open Firebug,
1) Select the Firebug icon that resembles a beetle.
Firebug opens in the bottom of the browser window.
To troubleshoot code,
1) Select the pointer next to the Firebug.
2) Mouse over the page to see the code.
At this point, you have a few simple choices to test and troubleshoot code.
3) Option A: Add css to the small window on the right hand side.
Option B: Add text to the main window.
Option C: Select a div tag or block of text >Right click the mouse >Edit HTML >Edit the html and test your new code. The changes will look as though they are live.