When I'm developing a front-end for a website, I put the name of the selector directly, for example .seletor1 , .seletor2 , and so on.
I recently had to work on the classes of a plugin I downloaded, and I saw that it contained: div.seletor
Excuse my ignorance, but I have six months front-end and have never used it like this.
I see two reasons for this:
You use the seletor class in more than one element type, and you want to create a CSS rule for DIVs only.
You need to give more weight to this rule in the CSS cascade. For example:
.seletor1 { color: red; }
.seletor2 { color: blue; }
Consider a <div class="seletor1 seletor2>... . It will turn blue (both rules have the same weight, but the second rule prefers to come later in the source code). So if you use
div.seletor1 { color: red; }
You can force the red color on this div.
When preceded by "dot" refers to a class and when preceded by "sharp", the famous "#" refers to an id.
The class should always be used when you want to set properties for a group of elements and the id for a single element.
When you set div.classe {} you can set properties for this class exclusively in this div.