Once a site gets a good pagerank, what imp. measures should be taken so that your pagerank doesnt go go below what it is now? Please give some tips
Continue to get links to that page - one of the few factors people talk about is that any good page of content will continue to earn links over time - since the quality should always be maintained. Try to get links to that page from authority sites.
If you sell text links and Google catches you or a competitor reports you they might penalize your site; this includes dropping your Pagerank value and preventing your site from passing on any Pagerank value to outbound links. To raise your Pagerank you need "quality" backlinks, these are links from "web pages" (yes, not websites) that already contain a Pagerank value and have little to no outbound links beyond your site.
PageRank is just a measure of link equity, thus to maintain it keep your link equity high. Eventually sites do drop your links or Google drops other sites, but either way, you need to keep pulling in links over time to maintain your PR.
Umm, no Pagerank is the probability that a web user will find your site if they keep clicking through links on the internet. Maybe you should learn about Pagerank before you try to educate someone about it. http://en.wikipedia.org/wiki/PageRank#Algorithm http://en.wikipedia.org/wiki/Probability_distribution = Who want to advanced there knowledge of probability algorithmic styles.
keep get high pr back links, do not sell links, do not cheange too much of the well done pages, try to design new pages.