Here is some more detailed explaination for what you see in the two videos:
In the first video you add
color: #33891b; as value for the
color property, which is wrong. Firebug does not allow you to add complete CSS properties or or even complete CSS rules within the
Style side panel. To do that you need to switch to the
Edit Mode of the CSS panel.
Note that the
Rules view of the built-in Firefox DevTools does allow you to add complete CSS properties (and even multiple CSS properties). And the upcoming version Firebug 3 will fully integrate into the DevTools, therefore it will inherit this feature.
In the second video you add a CSS rule with the selector
#footer a in the
Style side panel that doesn't match the
<body> element. The purpose of the
Style side panel is it, though, to show only the CSS rules applying to the element currently selected within the
HTML panel.
To edit the CSS style sheet with all its rules, you need to switch to the
CSS panel.
There are already
issue 5489 and
6902 filed to improve Firebug. And as Firebug 3 is a complete recreation of the extension on top of the DevTools, it will also have those features integrated (to some extend, as the DevTools also don't allow you to paste complete CSS rules including their
Rules view yet. Therefore I have created
bug 1224534 two months ago).
Best regards,
Sebastian