A site's PageRank impacts not only its ranking in Google search results but also the price it can charge advertisers. A drop in ranking can have serious financial consequences, especially for smaller operators. The search giant, through its dominant search engine and AdWords/AdSense network, is relied on by millions of websites not only for traffic referrals but for monetisation as well.

Many websites small and large receive over half of their visitors from Google search referrals. And without a sales team to sign advertising deals, most become AdSense affiliates, automatically connecting them with millions of advertisers worldwide. Ironically, in the ultimate democracy that is the internet, Google reigns as virtual dictator. By changing the way it ranks sites in search results, it has the power to effortlessly shape the digital economy and manipulate the incomes of millions of web businesses around the world. Yaro Starak, an Australian entrepreneur whose website, entrepreneurs-journey.com, provides tips on starting an internet business, recently announced he had earned $842 from AdSense in September alone. His total advertising revenue from the blog that month was over $10,000, but Starak's ability to continue charging so much is contingent on him maintaining high site traffic, half of which is referred by Google.

"Google controls the income source for a lot of people online, and we're not talking just search traffic we're talking pay-per-click [AdSense] traffic as well," Starak said in an interview. "Google has both sides of the fence - they've got the publishers, they've got the advertisers and they've got the search traffic, so that's why they're making so many billions of dollars in money each year."

Indeed, a whole industry has spawned with the aim of helping website operators obtain the highest rankings for certain keywords in search engines, and milk the most out of their AdSense accounts. But small changes to Google's algorithm that determines how high up in search results a site appears can foil any attempts to game the system in a heartbeat. The worst offenders who are caught trying to artificially boost their search ranking are given the "Google death penalty", whereby they're delisted from search results altogether. But it's not just illegitimate webmasters who are affected - even websites who do their best to abide by Google's rules can be impacted by changes to its algorithms.

Darren Rowse, a full-time blogger from Melbourne who also runs the b5media blog network, noticed the PageRank of a number of his sites drop significantly. He said it was too early to tell whether it will affect his site traffic or revenue, but he was more worried about the impact on his reputation. "It [the PageRank] does say something about my credibility and reputation - in a similar way to anyone ranking anything," he said.

Rowse has been hit several times over the past few years by changes in Google algorithms. One led to an overnight drop in his traffic by 80 per cent, which caused a corresponding 80 per cent drop in revenue. He said it typically took up to six weeks to build the site back up to its usual traffic levels. "For some bloggers it lasts forever and [the traffic] never comes back," he said. Google is tight-lipped about changes to its algorithms, but bloggers have speculated it made the most recent change to crack down on the buying and selling of text links outside the Google AdSense network. Many website operators pay higher ranked sites to link to them, in order to trick Google's computers into thinking the site is more authoritative and thus securing it a higher ranking in search results.

A Google spokesman said in a statement: "Values in the Google Toolbar can fluctuate for a number of normal reasons, including changes in how we crawl or index the web, or changes in the link structure of the web itself." The PageRank could be updated by Google to "to incorporate not only our view on the backlinks to a page or site, but also to incorporate our opinion of the forward links for a site".

Both Rowse and Starak advise website operators to become less reliant on Google for both traffic and revenue. "AdSense is very easy to implement so everyone does that - it takes a bit more effort to go and find an advertiser and set up a campaign with them ... but it does make you more stable," Starak said. While Starak diversified his revenue sources by selling text and banner advertisements directly to advertisers, he said if Google forced him to stop selling text links and delisted his page from search results he could lose as much as 50 per cent of his income.

"It's been said that Google owns the internet - it's not a permanent grasp but as long as everyone's using their search engine it's very hard for anyone to get in and compete with them."