Google demystifying false ideas about search engine

On the sidelines of the last roundtable between webmasters and Google specialists, during which the latter answered the questions asked by them first, Google released a slideshow of false myths and ideas about their algorithm (now removed from the site). This list is supplemented by information contained in previous releases .

Where did these false beliefs come from? Information spreads quickly, correctly or incorrectly on the Web. There is a share of beliefs that come from the complete inexperience of webmasters, but one share also comes from a misinterpretation of the algorithm, from what Google says very little, the main part of what is known is the study of filed patents, forced communication.
Even the engine involuntarily participates in disinformation, changing its algorithm: what it declares false can become true in subsequent versions!

French slideshow content:

Myth: You need to fill the page with keywords, fill it with meta tags and expose the site to the number of catalogs.

Myth: Mixing HTML and XHTML prevents Webmaster Tools from being validated.

Myth: It is important to appear in a thousand catalogs and search engines.

Myth: Participating in Adwords, AdSense or Analytics can help a site/or, conversely, punish it.

Myth: If a keyword is important, it is important to repeat it in important places on important pages so that they seem more important to important search engines (sic!).

Myth: Using XML sitemap can downgrade a site.

Myth: PageRank is dead/or, conversely, that's all that matters.

Myth: It's important to re-introduce your site regularly.

Myth: Once your site comes out on top, don't touch it.

Myth: Valid HTML or XHTML provides a higher position.

Myth: Using disallow in robots.txt will remove pages from the index.

Myth: The more connections, the better.

Myth: All that is important when you make a site is to lead in SERPs.

Myth: It is better to return the 404 error to old URLs so that the new architecture is discovered naturally.

Myth: It is important to use "index, follow" in meta-robots.

Placing a site on a mutual IP leads to the loss of positions.

Feel free to read the slideshow to the end, there you will find useful links.

Myths that actually came true

Although a slideshow dating back to 2008 describes them as myths, some false claims actually came true at the time!

Truth: Duplicate content will damage the site.

Truth: Social site backlinks have less value.

See also the roundtable report and Google's responses to webmasters.