I think I can help you with that!
First you need to understand of how the alphabet works. For a complete understanding of collating sequence, you can use this article for a head start.
http://en.wikipedia.org/wiki/Collating_sequence
Now, when you take a look at that article, you might find that for instance, the letter A comes before B and the letter D comes after C.
To change the order of tabs in Safari, one needs to left click the mouse and hold it down while at the same time moving it to another location.
I think it's best we take a look at an example.
(to keep it simple, I used 3 websites to illustrate)
If you've got the following websites loaded:
www.reddit.com
www.macrumors.com
www.google.com
The correct alphabetized order would be:
www.google.com
www.macrumors.com
www.reddit.com
Of course things can get really difficult if you have a lot of tabs open or if you would use a non Latin-derived alphabet or mix it up! ( I think I've seen someone doing that once, but he was Alphabet Boss!)
But these are the basics!
