While on-page optimization is a good first step, you will ultimately get much more leverage by having links from other sites to yours. Inbound links used to just be a source of referral traffic. Now, they influence your search
engine rankings as well.Google was the first search engine to use links as a significant ranking factor. They viewed a link from one site to another as a ‘vote’ for the target site. The more votes you have, the more authoritative your site is considered.
Specifically, there are two main benefits gained through each link:
1. Better SEO authority of the linked-to page and increase in authority of the site as a whole
2. More relevancy of the page for the keywords that are used in the link’s anchor text

Webmasters can add a ‘nofollow’ attribute to an outbound link in order to achieve this. Links from some popular sites such as Wikipedia, for example, are all nofollow. The way to verify
whether a link passes value is to check its HTML. This is achievable in different ways through different browsers but is generally doable.

Link Building with Head Terms vs. Long Tail Terms
Slightly different link building tactics may be required, depending on the competitiveness of a keyword.

Head Terms
Ranking for highly competitive head terms typically requires a more diverse source of links pointing to the appropriate page that targets the term. The links will need to use the corresponding keyword as the anchor text
as often as possible.
Mid and Long Tail Terms
Pages that target less competitive mid-to-long tail terms don’t typically require as many external links. Instead, sites can rank for these terms by gaining authority through strong, trusted links, often to the front page of the
site. Solid information architecture and good on-page keyword targeting will then provide the relevancy signals needed to rank for these terms. Most of the link building tactics discussed later in this chapter can be used either to target specific head terms or
simply to build the authority of the site, depending on your specific needs.
Tools for Link Research - It’s often useful to know about the links your site currently has. This information can help you make decisions regarding whether to aim for more links that will build site authority or to focus on deep links with specific
anchor text.Researching your competitors’ links can also be valuable, particularly in identifying link opportunities or niches that could also be useful to your link building campaign.

Yahoo! Site Explorer - Yahoo! provides a free tool that lists up to 1,000 of the links to any site. Enter your domain name or a particular page, select the ‘Inlinks’ button, and change the settings to ‘Show links: except from this domain.’ Also select ‘to:
entire site’ if you’d like to see links to the whole site rather than just a single page. These links are not in any particular order, and the list will include links that do not pass any value as well as
those that do.

Open Site Explorer - This tool provides information about the top 1,000 links to a site. These can be filtered to exclude links that do not pass value. Additional information about each link includes the anchor text used and the authority of each
linking page.The Open Site Explorer tool also includes reports that showcase the most popular pages on the site, the most common anchor text used to link to a page or site and other information about the strength of the page.