You probably know that you can drag a link from your browser to your desktop, creating a .webloc file, to make it easy to access a site in the future. But you can also use .webloc files to open such sites automatically when you log in.
To do so, create the .webloc file by opening the site in your browser and then dragging the icon next to the URL in the address bar to the desktop. Next, go to the Accounts system preference. Select your user account in the left-hand column, click the Login Items tab on the right and drag the .webloc file(s) into the Login Items list. The next time you log in, those sites will open automatically in your default browser.
If you add .webloc files to your list of login items, the associated websites will launch automatically whenever you open your user account