New York Times paywall goes live today

The nation's most prestigious general interest paper will now charge readers for extended access to its web site, NYTimes.com. In erecting a paywall, executives at the Times are trying to walk a fine line: generate subscription revenue from avid readers willing to pay, while still retaining more the casual customers who boost advertising revenue with their clicks.

Analyzing online readership habits and polling data led the Times to set that fine line at 20 articles every four weeks. Click on fewer and you'll have free access -- but to get article #21, you'll have to pay up.

Readers will need to shell out $15 every four weeks for unlimited online and smartphone content, $20 for online access and the iPad tablet app, or $35 for the full digital smorgasbord. (Print subscribers get it all at no additional cost.)

That pricing structure is subject to tweaking, according to Martin Nisenholtz, The New York Times' head of digital operations.