A client system is controlled for accessing protected remote resources via a Web Application using a rewriter proxy that supports relative URLs. In one configuration, the Web application can be a Portal application. A URL utility module can be provided for a rewriter proxy that splits an absolute URL into a base part (the URL string up to the resource) and the resource part. A security module computes an authentication identifier for the base part. This can occur by applying a secure hash algorithm and/or secret key. The URL utility module then constructs the rewritten URL by concatenating the URL encoded base part, the authentication identifier, and the resource part as separate path elements.