Your official organisational website or sites, that act as your online hub. Extra sites / subdomains that host separate functions such as a ticketing service or an online shop, should be measured separately - see the section on event booking and shop sites.

Framework Metrics
Size of audience Users, sessions
Engaged audience Engagement rate, average engagement time
Results Conversions, conversion rate, ecommerce revenue

Other useful metrics:

Metric Why?
Acquisition by channel See which channels (email, social media, search etc) are sending the most visitors to the site, and which are sending the most engaged and highest value visitors. Crucial data for allocating resources to the most effective channels.
New users Indicates audience growth
Page performance Look at the reports for important pages - this will tell you if people are staying on the page and for how long, clicking the calls to action, etc
User devices Understand which percentage of your visitors are using mobile vs desktop computers, and ensure key pages are mobile-friendly
Locations Important for understanding the audiences of regionalised programmes or promotions