Okay so I'm trying to get a dashboard to show up in a totally non-salesforce site (company intranet). My first thought was to right click on the dashboard grab the URL that is the source and use that as the source in my <img> tag on the intranet website. To my amazement, it worked, the dashboard showed up in a nonsalesforce site. After a bit of tinkering I have come to the conclusion that the dashboard only displays properly if I have another tab open in the same web browser logged into salesforce.

My Question: "How do I get Dashboards to show up outside of salesforce without making the user sign in  to salesforce somewhere ?"