I didn’t know this little fact, so I thought that I would pass it onto you.
When in Rome, do as the Romans do — don’t eat while on the Spanish Steps.
It’s forbidden to eat while standing/sitting on the Spanish Steps. Purportedly, there are signs showing this, but I have never even noticed this. You could be fined for eating on the steps, as much as 250 euro from what I’ve heard and read online.
Be mindful of signs when you are near cultural/historical sites and monuments, and always try your best to make sure that you obey the rules. Generally, the police will be forgiving with tourists, especially when they scream at you in Italian, and you have no idea what is being said. :)
*photo has been released into the public domain; original can be found here