Zero Article

When should we not use any article in a sentence?
I mean when is it appropriate not to use 'a', an' or 'the' in a sentence?

[Red5]

For a great summary all about the use of articles (including the zero article), see: http://owl.english.purdue.edu/handouts/esl/eslart.html

[Tdol]

It's used with uncountable nouns when you're not being specific

I like food. general
I liked the food last night. specific