Pseudo Selector First Child of Class

Problem

How do you apply a style to only the first element with a certain class?

.just-this-one {

background:blue;

}

<div class="top">

<div class="not-this-one">not this one</div>
<div class="just-this-one">just this one</div>
<div class="just-this-one">but not really</div>

</div>

:first-child does not do this, that just selects the very first child no matter what the class is.

:first-of-type doesn’t even do this.  but you would think it does, but “type” here implies the HTML element type like “div”, “p”, etc.

Solution

Use the tilde “~” to “undo” styles on elements where the class previously appeared.  So first apply the style you want to all .just-this-one elements.  Then apply “undo” that style for all subsequent elements.

.just-this-one {

background:blue;

}

.just-this-one ~ .just-this-one {

background:none;

}

This genius solution found on stack overflow (not the accepted answer):

http://stackoverflow.com/questions/2717480/css-selector-for-first-element-with-class

Additional note:  If you have a pseudo selector like :before, use something like the code below to write content before all li elements except the first one.

.menu li:before {
content: '';
}

.menu li ~ li:before {
content: "\002F\0020\002F";
color: #aaaaaa;
}