One of the essential components of the internet is the freedom to present information in any of the wide variety of available formats. The Yandex search engine aims to index and rank all available documents correctly. However, our robots may sometimes interpret something in a way that differs from what the webmaster intended:
Using <iframe>. For the correct ranking of a document, we don't recommend using the <iframe> tag, since the Yandex crawler does not index the documents loaded into it.
Redundant automatic redirection (redirects). If possible, avoid using redirects. A redirect can only be useful if the page URL is changed for technical reasons and you need to redirect the user to the new page. For more information, see Processing redirects.
Page URLs. Each page should be available at a single and permanent address. We recommend that the page URLs don't contain session IDs. If possible, also remove the CGI parameters.
Cloaking. Avoid situations when the content indexed by the robot is different from the content the user sees when opening the page. An example is site versions for different regions. Learn more about them in the “Region” section.
Images instead of text. Avoid creating pages that do not contain text. If the main page is an image linking to the main content and contains no text, it can interfere with site ranking. It happens because most external links usually refer to the main page. If it doesn't contain any text, the content analysis is less reliable.
Soft 404. A common mistake is replacing the 404 error message (page not found) returned for non-existent pages with a stub page that returns the 200 (OK) response. In this case, the search engine finds that a page with an invalid address exists and does not remove it from its database. This slows down indexing of useful pages on the site.
The site engine. Always check if the site software is performing correctly. Because of script errors, a page can have different URLs when the user navigates to it from different site sections. This can have a negative effect on the site indexing. In addition, errors in the "engines" can be used by hackers (for example, to place a link to a malicious site).
Learn more about indexing errors in Yandex.Webmaster.
The simpler and clearer your site is, the better it is indexed.