Do you mean Reader version 8.0? Or Designer version 8.0? In either case, both have been end of lifed for support. If you are looking for "bookmark" functionality in XFA, you will need the latest version of Designer, and LiveCycle products.
http://help.adobe.com/en_US/livecycle/11.0/Services/WS57a26560eb6a24db-6e5d73fa131760810bd-8000.2.ht...
If you are looking to just go to a URL, such as www.adobe.com, for example, you can use this script:
xfa.host.gotoURL(www.adobe.com);
/*
Retrieves the specified URL. It is available only for client applications.
void gotoURL(string param1 [, bool param2])
param1: The fully qualified or a relative URL. It is permissible to have a query string at the end of the URL. If the current document is being viewed inside the browser, or Acrobat Web Capture is not available, it uses the Weblink plug-in to retrieve the requested URL. If running inside Acrobat, then the URL of the current document is obtained either from the document's Base URL, or from the URL of page #0 (if the document was WebCaptured), or from the file system.
param2 (optional) : If True (the default), the resulting page(s) should be appended to the current document. This flag is considered to be False if the document is running inside the web browser, the Acrobat Web Capture plug-in is not available, or if the URL is of type 'file:///'.
XFA Version: 2.1
Availability: All
*/
Keep in mind, using the File:/// prefix to get to the local drive is a security concern.
