Get url value after hash tag

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jQuery

If the url below is visited and the value after the hashtag 'about' (Refer to link below) is found, I would like a specific function to be triggered. How would I achieve this please?

http://www.site.com/index.html#about.html

This method is a way I figured I could control an animated header in my webpage when the back and forward browser buttons are used instead of the main menu which would otherwise control its animation states. I hope this all makes sense.