Less and fewer have essentially the same meaning, but they are used differently according to what they modify. Less is used with mass nouns, while fewer is used with count nouns. Look at the following example:
Example (less-correct usage): There is less milk than juice in the refrigerator.
In the example sentence above, milk does not consist of an amount that can actually be counted, so less is the appropriate word to use. This type of sentence rarely causes any problems for English speakers. However, in a sentence such as, “There are fewer people in class today than there were yesterday,” a great deal of confusion arises over what is correct. Many people would be tempted to say, “There are less people in class today than there were yesterday.” But remember that if the objects can be counted, always use fewer, not less. People in a class can be counted, so fewer is the correct choice for this sentence.
@Marv Higgins: I was so relieved to read your post and realize that I’m not the only grammar snob! I was appalled when I saw Red Lion’s billboard, and I had the same thought…I will never stay there! Thanks for making me feel *less* crazy!
My favorite error is found at every grocery store: “10 Items or less.” Way to go Wal-mart!
How about all the beer commercials that say “Less Calories”? We all can count calories. In school, I learned the difference from an example given: There is less sand on the beach after a storm, but there are fewer grains of sand. You can count grains (or cups,or spoonfuls,etc.), but you can’t count sand in general.
I will never stay at a “Red Lion Inn” because of their grammar. They advertise that we can “count less sheep” – is that so we can have sleepless nights? I would rather count fewer sheep, and not have countless sheep to count.