:target

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Selects an element that is a target; i.e. that has an ID with the same value as the URL's hash.

Testsheet:

p:target {color: #CB000F;}

This paragraph has id="testHash". If you target this by #testHash it should become red.

Once you’ve done that, use the Back button to go back to the previous state. The paragraph should lose its red colour again.