Favorable ou unfavorable criteria of the algorithm

List of criteria which will let you getting a better ranking in search engine results.
Four factors are essential for the ranking of a page in search engine results.

Coding:
+ Favorable factor.

- Unfavorable factor.

Hosting

+ Geolocation: the host is located in a country corresponding to the language of the site or involved in its activity.

- Frequent interruptions of service.
- Slowness.

Domain name

+ Contains keywords in the topic of the site.
+ A generic top-level domain (com, net, org, biz) matches the type of site. Net worth to an activity of network and org to a non-profit activity.
+ Or it is the language or the location of the site, for example fr for a site in french, us for a site about the United States.

- Is redirected by a frame on the host.
- Too long name.
- Contains a trademark name (it might be withdrawn).

Topic of the site

+ Start your website with a well-defined and measurable goal. Choose precisely the topic.

- Addressing various topics in a same site is bad.

Site structure

+ Hierarchical organization: homepage-> main topics. Topics -> articles.
+ Name of subdirectories corresponding to the topic of the content.
+ Presence of a robots.txt file.
+ XML Sitemap linked from robots.txt.
+ Presence of an RSS feed.

- Using frames.
- Sub-domains rank less then sub-directories.

Organization of a page

+ Title into a H1 tag. It can describe the content of the page or be addictive.
+ Subtitles in H2, H3, etc. tags.
+ The headings and subheadings contain keywords, about the page for H1, about the chapter for H2.
+ Using style sheets.
+ Place CSS and JavaScript code in separate files, to speed page load and to emphasize the content.
+ Use em (emphasis) and strong (bold) tags, they are equally important to highlight keywords for ranking.

- Too large-size text or file too heavy to load.
- No text in the page (images only).
- Too many ads, over 10% of the space.
- Using H2, H3 in sidebar for layout (see Wordpress themes).
- Lack of a charset.
  Its format is (iso-8859-1 may be replaced by UTF-8):

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

- Hidden text or hidden links in the code of the page.
- Using tables, presentation attributes of HTML as font, color, etc.

The title tag

+ The title tag is mandatory. It can be the title in H1. On the home page, it may include the name of the site.
+ The syntax is <title> text of title </title>, and it occurs in head section of the HTML code of the page.
+ It contains the main keywords representing the content of the page.
+ The most important key words are preferably at the beginning of the title.

- Same text in the title on all pages.
- Text made of a series of keywords.
- Text beginning with the name of the site on all pages.

The description meta tag

+ It can be used for description displayed in the results pages of search engines.
+ Size less than 160 characters.
+ The text must be appealing but not as an advertisement.
+ The format is: <meta name="description" content="...desc...">

- Description made of a series of keywords. Rather, it must contain true phrases including keywords.

The canonical attribute in the HEAD section

+ Avoids duplicate content problems and gives to search engines the unique URL to use for their index. The format is:

  <link rel="canonical" href="http://www.scriptol.com/current-page-url" />     

URLs of pages

+ They are explicit and contain keywords corresponding to the content.
+ Shorter are better.
+ Use hyphen for separators.

- They are numbers.
- Include parameters and session ID.

Keywords

+ The page must contain all the keywords representing the content and all the synonyms.
+ Keywords at the beginning of the article weigh more for ranking.

- The "density of keywords" is not a criterion for true optimizing. Needless to multiply the same words.

Images

+ Presence of an alt attribute that describes the image.

<img alt="" >

External links

+ The correct form is:

 <a href="absolute url "> anchor </a>

+ Links to quality websites.

- Remove broken links. Use regularly a tool for automation detection, see in scripts.
- Using nofollow (external link are a part of the value of the page). PR is not shared between other links, it is share between ALL links.
- Links on pages unrelated to the source.
- Links to dubtious websites.
- Same links repeated in footers.
- More than 100 links in a page.

Links between internal pages

+ The URL is an absolute address whose a part is the name of the site and the protocol (http://).
+ This text is a description of the target page and it contains the main keywords of this page.
+ Link in the content are better for ranking than links separated of it (in menus for example).

- Dynamic JavaScript links.
- Using nofollow (that means the link is not taken into account by search engines and lost in PR).
- Avoid 302 redirects.
- Avoid absolutely double redirects (redirect to a page redirected itself).

Backlinks

+ Backlinks of reference sites or pages with a high PageRank.
+ Backlinks from page with few links.
+ Presence in the Dmoz directory and the most important ones.

- Sudden increase of backlinks by inscriptions on many directories.
- Source of backlinks are only directories or sites where one add oneself the link.
- Numerous backlinks from only some websites.
- Using the same title and the same description in the submission to directories.
- Link exchange with blacklisted sites, which lost their PageRank.
- Links from satellite pages created for this purpose.
- Loss of backlinks without replacement by newer ones.
- Buying/selling links.

Social networks

page with an author name having a Google+ profile ranks better in SERPS.
Was viewed like a ranking factor, but then was denied (Ref SMX 2014).
SERPs show your profile image when the site is connected to G+, which is suitable for a blog but not for products. Your link could by ignored.

See also this online tool to check a page, Website diagnosis toward search engines.