Do you have one of these watermelon carriers? I didn't think so.

Several weeks ago I passed this restroom door, which was located in a grocery store. Cannot?  Oh yeah?  That sign made me want to prove the sign wrong by carrying tons of merchandise into the restroom until it was completely full of merchandise. I don't know why the "can" vs. "may" error gripes me so much--perhaps it's because I hear and see this problem so often, and also because it seems that it would be so very easy to understand the problem and stop making the error.

There's a Wikipedia article on words without vowels and words without vowel sounds.