Disclosed are various embodiments for separating control of network sites through the use of a proxy server application. A proxy server application obtains a request for a network page associated with one customer out of several customers of an organization. Each of the customers has an online presence hosted in a trusted network. The trusted network is subject to security supervision by the same organization. It is determined whether the network page is within a customer-managed portion of the network site. The network page is obtained from an untrusted network that is not subject to security supervision by the organization when the network page is within the customer-managed portion of the network site.