This is the feature many SFDC Admins have been asking for. Currently it is not possible to refresh the dashboard automatically when the sfdc user logs in to salesforce.com.
Use the following steps to refresh the dashboard( automatically…after 5 seconds) when the user logs in to the salesforce OR the user clicks the home tab:-
1) Create a new custom Home Page Component( type:HTML)
2) Add the following code:-(click the show html button before pasting the code)
3) save and Add this component to your Home Page Layout.
quite simple….right?? 🙂