If you have a Google account, you can save this code to your Google Drive.
Google will ask you to confirm Google Drive access.
Save file as:
If you have saved a file to Google Drive, you can open it here:
You can not style a pseudo-class on a particular element, but you can get the same result by creating a class in your STYLE section (or stylesheet) and add that class to the specified element.
Click the "Try it" button to add the class "myClass" to the DIV element: