The supporting processes perspective is the perspective which shows the strategic processes that are not directly client-related, but may be strategical in the primairy process.
Example are administration processes like stock and finance, or transport. They are not crucial for getting the order but it will affect the company and website badly if they are not working good.
Also in this perspective belongs the websitemanagement which will control the performance and the adjustments to the website.

Like the customer orientated processes, the definition of these processes depend on the specific company and website the webscorecard is being made for.