Every user should be prompted (most ideally as part of the web browser setup process) to sign up with a micropayment processor, and to support the websites they use.
Every so often -- say once a month at a minimum -- the user should be prompted in some way with a report saying "here's the $ of total payments that have been requested for websites you visited since your last payment."
The user should be able to adjust the total amount up or down (adjusting each site's amount proportionally) and to drill down and modify or zero out individual sites.
Separate from this, the user should be able to specify in preferences:
Regardless of the settings above, every site HTTP payment request would be logged, and accessible in the regular payment report.