How to add css selector in firebug' style's area?
firebug
Solution
You can right click on Style Tab then Edit Element Style... or New Property...
You can also enable/disable styles by clicking a RED Circle with diagonal line. If the style becomes grayed it means that it is disabled.
Problem
How to add new css class or id and then write properties for html element in firebug's right side css pane. like we can write in web developer toolbar > edit css