I can not find solution - how to check really weight and quality of back link for google ? I want buy only quality links. And links with high PR not always really have good result. How to check quality of back link before buy link?
Well age has an important factor. If the domain is old (ie registered in 2000) then this would be a good quality link. How many other outbound links are on that page? The lower the better. This can be checked with a firefox addon called SEOQuake. Relevance is also very important. Does the page where the link will go have relevant information to that on your website. Links from a sports site to promote a sports site is extremely higher quality than that of links from a pets site.
It's up to you to define quality. Forget about Google and focus on links that appeal to your target audience. If you are buying for SEO purposes you will likely not be able to buy enough to make that much of a difference unless you have a really large budget. How would you judge the quality of the site? Let that be your guide.
I personally do not buy links, but if you choose to , ask the seller for what keywords does the page you interested in is ranking high. For example: if you are interested in links from real estate niche, make sure the page you are about to get link on is ranking for real estate terms.Then you know you have a strong link on related site, and the PR does not matter at that point. Also go and check "related:" operator in google, it will show you how goole see this site and if it really represents the niche it says it does. see more about checking for quality links here: http://www.askfrank.net/links-exchange-tutorial.php
You need to take some of these factions into consideration: Domain Age, Niche relevancy, PR, Outgoing Links, Backlinks of the page, SERP of the Page etc..
just buy link of websites having good traffic also because only PR is not important for a quality linking
Make sure the website is relevant to your niche, old enough and does not have a lot of outbound links. You might also want to check its traffic to make sure youll get some visitors.
Check age and if the website is authority website for its keywords. Number of links on the page matter. Content link is good.