In this paper, we propose a client side information management method for web services collaboration. Recently, personalization is one of the most challenging topics of the web technologies such as targeted advertising and LPO (landingpage optimization). On the other hand, many types of the web contents collaboration, which is called mashup sites, are developed. The purpose of the proposed method is to realize web contents collaboration and personalization simultaneously. Since one of the essential problems to realize the web contents collaboration is the mechanism of processing personal data. We design the mechanism of the personal data processing with client side procedures. In the proposed method, HTML documents of the websites need to be slightly extended for the web contents collaboration. With the proposed method, web contents collaboration with personal data is realized without the exchange of personal data. We implemented this method as a local proxy server, for a user can set the proxy server on the ordinary web browsers.