HTML and CSS Reference
In-Depth Information
•
Creative Commons Attribution Non-Commercial Share Alike (cc by-nc-sa)
Creative Commons Attribution Non-Commercial No Derivatives (cc by-nc-nd)
•
You should select a license that matches what you let others do with your work (distribute commercially or
noncommercially, remix, tweak, share with proper crediting, alter, and so on).
The profile of this microformat is
http://microformats.org/profile/rel-license
[40], which can be specified
on the
head
(X)HTML tag as shown in Listing 7-15.
Listing 7-15.
The Head Profile of
"rel=license"
<head profile="
http://microformats.org/profile/rel-license
"
>
rel=“nofollow”
One value of the
rel
attribute deserves extended attention, because it is often used in
search engine optimization
(SEO).
When
rel="nofollow"
is added to a hyperlink, the link destination should not be considered for additional ranking by
search engines. This attribute value can be applied if document owners need hyperlinks without affecting the ranking
of their web pages or links to external web sites. For example, if a hyperlink is vital on the web page but its destination
page has a very low PageRank, the hyperlink should be provided with
rel="nofollow"
to avoid search engine penalty.
■
pagerank (pr) is a link analysis algorithm used to assign a numerical weighting to each web document in
order to express its relative importance on a 0-10 scale.
Note
For example, if
lowprsite.com
has a low PR but you have to link to it because of the content presented there, you
can use the
rel="nofollow"
microformat as shown in Listing 7-16.
Listing 7-16.
A Link That Will Be Not Considered by Search Engines While Indexing a Page
<a href="
http://www.lowprsite.com
"
rel="nofollow"
>Low PR site</a>
Listing 7-17 shows the profile URI of this microformat.
Listing 7-17.
The Profile URI of
rel="nofollow"
<link rel="profile" href="
http://microformats.org/profile/rel-nofollow
">
Although it is widely used, there are several open issues about this microformat [41]. The
rel="nofollow"
microformat indicates a behavior rather than a relationship, so the definition is illogical. The name of the microformat
does not reflect the real meaning. It is not a noun. It does not affect spamming. Finally, many legitimate nonspam
links might be ignored or given reduced weight, which is an unfortunate side effect that should be eliminated [42].
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