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Just go to http://iwl.me/ and put in a sample of your writing and voila! It tells you. It also can be different depending on what you put in there. I suggest prose vs. pointing out different web sites.
This site is trending right now, has gone viral, and is very popular. And fun!
-Betsyanne
My Personal Page and blog
The Nontrads site and blog
My Squidoo pages
Join me on Twitter as @betsyanne or @nontrads