I am making a page with a CSS lightbox-type effect using the :target pseudo-class. When you click on an image, a box pops up with info in it, and goes away again when you click
The pseudo-class target works on id elements, not classes: https://developer.mozilla.org/en-US/docs/Web/CSS/:target
The :target pseudo-class represents the unique element, if any, with an id matching the fragment identifier of the URI of the document.
Try replacing your .lightbox with #lightbox in your CSS, and your HTML element should be #lightbox {
display: none;
position: absolute;
z-index: 8;
width: 100%;
height: 100%;
top: 0;
left: 0;
background: #fff;
padding-left: 30px;
}
#lightbox:target {
/* Show lightbox when it is target */
display: block !important;
outline: none;
}