The invention achieves internet-based collaboration without having to install collaboration software on one of the computer. For example, a customer of a bank would like to collaborate with an agent of the bank. The customer accesses an external web server via a collaboration server. The collaboration server replaces a transition destination URL of HTML code acquired according to a request from the customer with a character string including a host name for the collaboration server and transition destination identification information and sends this character string to the user. When the customer clicks a link, the actual URL to be acquired is specified from the transition destination identification information at the collaboration server, and this URL is acquired by proxy and returned to the customer's browser. A browser monitor program then monitors the agent's browser, the URL to actually be acquired is specified based on transition notification from the collaboration server and the same HTML code as for the customer is acquired.