Visits Field
The Visits field of the SPSite.UsageInfo structure contains the cumulative number of visits to the site collection, which is tracked by the usage analysis code.
Remarks
Visits are defined as hits that have a referring URL from outside the site or no referring URL at all.
The usage analysis code tracks only what is recorded in the HTTP logs. HTTP logs record most operations except requests for files in the _layouts directory and HTTP requests with results greater than or equal to 300 bytes.
Requirements
Platforms: Microsoft Windows Server 2003
Security: Code Access Security