Green tags in Safari indicate Extended Validation SSL in use.
Since updating my copy of Safari to 3.2.x, I’ve noticed a number of vendors that offer online ordering now have a little green tag with the company’s name next to the lock icon that Safari uses to indicate that a site is using SSL.
After a little Googling, it looks like Apple has implemented support in Safari for recognizing Extended Validation SSL certificates. EV SSL certificates essentially indicate that the vendor in question has gone through an audit process with Webtrust and adopted approved standard practices for certificate validation. In other words, it’s a certificate that’s supposed to make your customer trust you more because you’ve put more effort into protecting the customer’s data from being compromised.