Originally Posted by david64
More traffic will help improve your Alexa rank. Best way to do that is to produce interesting content on a regular basis, particularly if you can provide really valuable and sought after content.
Technically, Alexa doesn't measure traffic. It measures visits from people who have the Alexa toobar installed. Very different, because the majority of your visitors likely don't have the toolbar installed (or even know it exists) unless your site generally gets a lot of visits from your fellow webmasters or technical people who are already familiar with Alexa.
This leads to a lot of "skew" in the results, as sites that cater to a webmaster/technical crowd get credit for proportionally more traffic, while those that cater to a less tech-savvy group (that is, the majority of sites out there) get credited with proportionally less.
Bottom line, unless the visitors you get also happen to have the Alexa toolbar installed, more traffic in and of itself won't help you with Alexa.
The easiest way to get a higher (or technically, lower) Alexa rank is to install the Alexa toolbar for yourself, and get a couple of friends to install it, and then all of you visit your website several times a day.
You'll be amazed how quickly and how far your Alexa ranking will improve.
This is what is meant by the number being easily manipulable. It's laughably simple to "game" Alexa, and many, many website owners do so.
As to using Alexa rankings for selling advertising, I'm sure you can use Alexa rankings to "prove" your traffic for some less knowledgeable advertisers, but if you're working with anybody who knows a bit more about How The Internet-webs Thingie Works, you're likely going to have to provide something more reliable.