We all know the importance of external links to SEO, which is undoubted. Especially when optimizing popular keywords, all that people doubt more is what kind of external links are good links.

Below from the comparatively idealized situation to see which conditions are required by good external links?

Whether the relevance of content exists between link website and your website or not

If the content of opposite website is totally different from that of your website, even though link with your website at home page, it is not very helpful for your ranking. Certainly, in case that the PR value of opposite website is quite high, then the advantage led to you is that the PR value of your website will be correspondingly increased, whereas what we shall pay attention to is that the PR value showed on Google Toolbars is not real and it has no direct relationship with ranking.

If you just target at the improvement of ranking of relevant keywords, you'd better look for some connected website links.

How about the ranking of link page

Where is the website linked by opposite party when searching your targeted keywords? The higher ranking is, the higher value of such a particular website in search of specific keywords is, the greater influence of given link on you website ranking is.

In case of the commercial keywords, the top websites may belong to your competitors, so it is impossible to link with them. However, you can keep your eyes on top one hundred, even two hundred. For search engines,  weights of these websites aiming at the specific keywords are all heavy, although users cannot see them commonly. Among such top one hundred or two hundred websites, there is often a large number of non-commercial and non-competitive website.

How about the overall ranking of link website

 To see the targeted keywords of opposite website, then search these keywords to see the overall ranking of this website. Similarly, top twenty is not required here, just top one hundred or two hundred is enough. The overall ranking of website reflects the weight of such a domain name in the eyes of search engines.

What is your given link text

Surely the best is the targeted keywords you hope. If the link text is something like “click here”, effects may be significantly reduced.

So mention one more time, link text is quite important.

Place of link

Link in the text of web page makes the best effect. If in hub page or commonly in the place of sponsored links, search engines can judge that it is not a part of content. If in the text, it is most possible for article to vote.

Overall condition of website health

It involves Google PR (I know, Goggle PR, rarely valued by many people, has no direct deal with ranking, but it is better to have a look.), Sogou Rank, date of domain registration, whether DMOZ is included or not, how many external links the website totally possesses. Examinations of such health condition benefit the guarantee of link website's weight.

How many back links exist in link pages

Internal links and external links are included.

If weight of opposite website is very heavy, while the link page given to you is jut for friendship link, opposite web page seldom link this friendship link page, and then weight gained by the link page will be greatly reduced.

If link page is normal content page, the same as other web pages except the acquired internal links, in case of good content, there may be lots of external links, the more, the better, and Yahoo can be used to search back links.

Number of back links in link page

As you all know, with the increasing number of back links in particular pages, weight carried by each link will be separated. If only several back links, your weight will be correspondingly increased.

Alexa Ranking

Many times, external links not only bring about the link weight, but also the actual traffic volume, so it becomes necessary to see Alexa ranking of opposite party, and moreover, attention should be paid to curve to prove that it is the naturally cumulative curve or acquired by cheat.

On condition of achieving high marks in the aspects listed above, such external links are best of all that only come out by accident.