Improve and Optimize search engine ranking

Is it a good practice to buy links?

Yes it is good to buy links if the following conditions are met:
1. search engines do not treat these as paid links,
2. links are from relevant pages, and
3. there are not more than 20 outgoing links on a page. We place our search results behind captcha pages where search engines cannot get information of our partner sites and are thus not able to crawl them.

How does it help my site to get links from contextual pages?

Contextual pages contain informative content for the customers. Search engines love such pages and treat them as natural. Contextual links may also be counted as editorial or external references (as in Wikipedia) and can get high relevancy score. Placing links on contextual pages can help in improving the rakings of your website to a considerable extent. On the other hand, if your links are placed on a web page full of outbound links, it will be of no value to visitors, and so, can bring your PR down.

How many outgoing links are there on each of these pages?

There are less than 20 outbound links on each of these pages.

What is the minimum number of links I need to buy in a single shot?

You have to purchase minimum of 5 links in one shot.

How many maximum links can I buy in one shot?

You can buy 500 links in one shot and as many as you want in one order.

Is Page Rank the most important quality parameter?

Page Rank is certainly one of the important parameters but there are other parameters also which are equally important (or more in some cases). Relevancy of the page content, anchor text, number of outgoing links on the linking page, domain and page authority, link age are some of the other significant parameters.

Can I get links from Unique C class IP and Unique IP addresses?

Yes, you can get links from Unique IP pages or C Class IP pages.
For more details, visit http://www.links-builder.com/buylinks/how-to-purchase-links.php

How will I know that my links have been placed on these pages?

Once you will finish your purchase, you can check all the details in your LinksBuilder dashboard.
For more details, visit http://www.links-builder.com/buylinks/how-to-purchase-links.php

Does the linking website as a whole should be on the same topic as the targeted website and not just linking page?

Though it does help having the whole website dedicated to your industry segment, however, it is the page content that should closely match your product segment. For e.g. Wikipedia, news websites, top directories such as DMOZ, all have page level relevancy and not the domain level relevancy.