I'm really not one to poke fun at people's grammar mistakes (notice the proper use of apostrophe). Particularly, because I know I use commas way too liberally. I enjoy run-on sentences; it's how I speak. I love dashes. I don't always get my verb/plural/tenses matching. I can't spell to save my life. And lots of other lazy, stupid things. All that aside, I don't think I would have made THIS mistake:
Painter's in lobby, please be careful
The sign was taped to the inside elevator doors at SCHOOL.
If anyone wants to read a fun grammar book (and I think this book should be used in high schools around the country) pick up Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation