If you plan to save your TaskMaps as web pages, you must ensure that your hyperlinks will function both from within Visio and from within the published web pages. The key to maintaining link integrity for relative hyperlinks lies in understanding how Visio stores hyperlink address information. For better or worse, this topic gets a bit technical but once you understand the basics, you’ll be able to take advantage of the considerable flexibility that relative hyperlinks provide.
For a simple example, refer to Sharing Web Pages. For more complete information, read What is the Hyperlink Base?, along with Creating Relative Hyperlinks and Using Relative Hyperlinks.