Is there such a thing as a free newspaper?

In the article linked to below from Slate magazine, Tim Harford, the author of the Undercover Economist, looks at how newspapers are approaching the pricing of online versions of their newspapers and articles. Why is it that all the articles we link to in these news items are free for you to read? How is this sustainable for the newspapers?

Why you didn’t pay to read this MSN Slate (27/11/07)

Questions

1. Explain the different pricing models that are available for newspapers when pricing the online versions of their papers.
2. Discuss the extent to which a newspaper website is a complementary product to the printed version.
3. Assess the extent to which competition between newspapers has driven the pricing strategies they have adopted for their websites.