How to create ID´s and Classes to address specific items in the theme ?

Hi Flynn,

you recommended me to use firefox with extension to work on your theme css and customize it. That recommendation was super ! Thank you very much ! Without this tool I would be totally lost !

But now comes my latest question:
When I want to edit an item, it does not always has it´s own class or id. So if I edit it, I automaically edit all items in that class or with this id.

Example:
In the right sidebar I have 2 widgets. Each with a headline. Now I only want to have the headline of the upper widget with a border under it. When I add border-bottom to the div.widget-title in styles.css, all titles of widgets get a border.

How can I create for this single title a class or id, so that I can define css only for this specific item ?

That would be very important to know for many situations. Sometimes I also get no class or id shown in firefox. Just element.style (geerbt von p) z.B.

That brigs a lot of headaches to me.

Thank you for support, even if it is not specific for your theme. I am sure many people need such infrmation here.