To vertically align :before and :after pseudo-elements, you can use the vertical-align property. Here's an example:

css:

div:before {
 content: "Before";
 display: inline-block;
 vertical-align: middle;
}
div:after {
 content: "After";
 display: inline-block;
 vertical-align: middle;
}

In this example, we're using the :before and :after pseudo-elements to add some content before and after the div element. We're setting the content property to some text and the display property to inline-block so that the pseudo-elements behave like inline elements and can be vertically aligned using vertical-align.

By setting vertical-align: middle;, we can center the pseudo-elements vertically within the div element. You can adjust the value of vertical-align to achieve the desired vertical alignment. Other possible values for vertical-align include top, bottom, baseline, and numeric values such as 50%.

Note that vertical-align only works on inline-level and table-cell elements, so you may need to adjust the display property of the element to make it work properly.