What I am going to say in this post will run afoul of everything that any SEO will ever tell you, but it is completely and utterly absolutely true, and I can prove it with numerous websites!
There is an old joke about a man who comes across another man, searching for his wallet under a street light. The guy tries to help, but in a while it becomes obvious that the wallet is no where to be found. So he asks the other guy, "are you sure you lost it here?" The original searcher says: "No, I lost it in the ally, but the light is better here!"
If you are an advertiser, seeking to sell something, there is a lesson to be learned here. If you choose which sites you want to place your ads with, based on page or traffic rank. you may be searching in the wrong place!
Page and traffic rank, are quite simply gauges, like the fuel gauge on your car. They give you an amount relative to the capacity of your fuel tank, but like fuel tank gauges, they can be inaccurate, broken, or deliberately miss calibrated. If you have ever been stranded as a result of a fuel gauge being inaccurate, you already understand this. Page rank tells us what Google thinks of the importance of a given page, that is the amount of fuel that Google thinks you have. The calibration is set by some factors which are mostly unknown to the average webmaster. The one known factor being links which unite your page with another. this is seen as being important, because it is a metric to tell what others think of your page. There is also a provision of some sort to determine the relative importance of these links, that would be their measurement of fuel quality. Recently this has been a matter of debate, since this gauges one known measure of importance can be affected by buying links, and if this is done, the actual amount of fuel in a tank can not be measured accurately.
Traffic rank is a gauge used to measure traffic, of course. That is the numbers of people visiting a sight. It is impossible to measure the quality of the traffic. There are several tools used to gauge this, and most of them are vulnerable to misunderstanding of one type or another. To put all of this in perspective, let's just say, that neither is very good at doing what it is intended to do, which is to tell you what condition your condition is in.
Is there a gauge to tell what is really going on? I would say yes. The true measure of success is whether or not a page is accomplishing it's intended purpose. This can be one or more of several things, such as conversion. Are people coming to my site and doing what I want? Are they viewing, buying, taking a particular action, for which the website is designed? If the sight is designed to be a catalog of materials and services, are people coming there and seeing what you want them to see? Is it designed for providing information, selling advertisement etc.? If so, is it doing this?
This assumes that the page is visible to viewers. If you are using the site to describe services that your company provides, by sending people to your site from the outside, using such things as business cards, print ads, adwords, fliers, etc. and that works for you, then you have reached your goal. Most of us will use a combination.
Where does my page appear in the search rank pages, when someone types in a keyword? This is what really matters. It does not mean a thing if you have a page rank of seven, but no one can find you when they type in your search phrases. The same is true of traffic rank. If your graphic line is flat, yet you can be found by someone who is typing your business phrases into the browser, then you have success.
I know a site, with several of the pages ranked at two on the green bar, which can be found in the number one to ten slot by typing in almost any word related to the industry. In this case, page rank effectively means nothing. Now, if you are an advertiser, and you want your ads found in that industry, you can go to the dozen or more sites that rank higher in PR, or you could go to the one that is constantly ranked above the rest for searches that are related to your business. Even if the traffic rank was a true measure of the eyes coming to a given site, the traffic would still not be as well targeted Frankly, I am astonished that advertisers haven't figured this out. If and when they do, it will change everything.
Saying: "This website ranks higher, so I want to advertise on it," is tantamount to saying; "I lost my wallet in the ally, but I want to search for it in a place where there is better light!" Page rank as determined by Google, or traffic rank as determined by Alexa, amounts to opinion, and these opinions are basically irrelevant. The only truly significant measure of a page, is whether it can be found when a related search is performed.
Content is King, and getting links by using content, wont get your website banned!