When it comes to search engine optimization, not all links are created equal. Google has long relied on back-links to determine a page's popularity and influence its rankings, even after the infamous Penguin update. Of course, people tended to abuse the system, spamming links anywhere they could input text online. In response, search engines began recognizing two different types of links: no-follow and do-follow. Each has its own place in your SEO strategy, but it's important to recognize their unique traits and plan accordingly while improving your business' visibility.
Do-follow links are the most useful links for SEO purposes. When a Google indexing bot travels down a page, it explores any links it comes across and makes note of where they are going. This is how new websites first get indexed and partially determines how often your site is crawled.
When it comes to do-follow links, quality is now preferable to quantity. A back-link from a high-quality website is a substantial mark in a page's favor and likely to boost its ranking. Meanwhile, a link from a low-ranked page has little effect, and hundreds of spammed links can actually bring down the wrath of a vengeful Google. Using do-follow links on your own website promotes discussion, but you may find yourself drowning in spam. All links are automatically do-follow unless specified otherwise.
A no-follow link, as its name would imply, instructs a Google bot to skip right past the link and continue indexing the page. At first glance, its easy to think that they are therefore useless to Internet marketers, but sometimes a no-follow link is worth just as much as a do-follow.
Many blog commenting systems, forums and member-driven communities use no-follow links to discourage spamming. A link from these sources is of little use for SEO, but it can drive substantial traffic to your site, and there's speculation that no-follow links are still given slight consideration by Google. No-follow links are created by including a small HTML tag with the link.
Practical Uses in SEO
No one wants to waste time when working on SEO. Time, after all, is a valuable commodity when you have a business to run. Because of this, knowing when a back-link is worth pursuing is critical. Do-follow links should be the primary focus of webmasters looking to boost their page rank quickly. They offer the "link juice" needed to boost a website's profile with Google. A no-follow link from a website or blog with a substantial readership, however, should not be turned down. In the end, a balanced mix of both shows Google that you aren't just building links to game the system, and may be the most lucrative solution of all.