I've been noticing something.

www.webhostingtalk.com
http://webhostingtalk.com

Have different PageRanks, now, what's the best one to link? With or without the www?

There's no best, if it works it's fine. I think the ideal way to link to a home directory is http://domain.com, since 'www.' would imply there's a subdomain.

It all depends on your objectives, really. If page rank is an issue, the site to which you are linking will want to choose one form or the other, and will want to permanently redirect the other one to it. I happen to think www. is the right way to go. It's understood it only denotes subdomains if anything else is there.

If page rank doesn't factor into how you're linking, as Paul says, it really doesn't matter which one you choose.

They have different PageRanks because they're different urls and potentially different pages. I used to be able to illustrate this with the example of one fairly well-known company that had their consumer site at www.example.com and corporate site at example.com -- but they've changed it and I haven't found another example.

So the best approach is to choose one, and use that url for any incoming links you create or solicit. Use a 301 redirect for any requests to the other one.

As to which one to choose, it's to a large extent just a matter of taste -- but there's one potential problem with choosing the "wrong" one, if UseCanonicalName is set to "on" on your server... in which case the version you use should be the same as your server alias.

If you don't know what that value is, the easiest way to check is to view a standard 401 (request a page at your site that you know doesn't exist) or other server error page. As long as you're not seeing IE's "friendly error pages," (near the bottom of the page there's be a line that ends with one version or the other of your domain name... something like "Apache/1.3.33 Ben-SSL/1.55 Server at webhostingtalk.com Port 80." If you don't see that, either use a different browser or turn that "feature" off in IE. Then either stick with that version, or change your server alias (or ask your host to do it).

I use www. :)