So this is how pedantic I can be. I tweeted my last post by saying "The words of my mentor, Tony Ciprian, in 140 characters or less".
Of course, that should actually be fewer, not less.
And so I'm writing a whole new post to correct myself, and to explain the theory!
It appears a lot of people don't know how to use the two words. I didn't for some time. But now I find myself shouting at the television whenever I hear broadcasters and guests using the wrong word in the wrong situation.
The basic rule is can what I'm talking about be counted?
And if it can, you want to go with fewer.
Are there less cars on the roads today? No, there are fewer cars on the roads today... because cars can be counted. However you could say there's less traffic on the roads... because traffic as a whole can't be counted.
Less cake? Yes, but fewer slices of cake.
Fewer raindrops... (admittedly not something you'd often say)... but less rain.
Less of a crowd. Fewer people.
Does it all make sense? Good. Now make sure you use the right one!
More here from Grammar Girl at quickanddirtytips.com