Search engines do have algorithms for consolidating mirrors and pages with the same
content. Sites with session IDs should, therefore, be recognized and indexed correctly.
However, it is difficult to index such sites and sometimes they may be indexed
incorrectly, which has an adverse effect on seo page ranking. If you are interested in seo
for your site, I recommend that you avoid session identifiers if possible.
Redirects make site analysis more difficult for search robots, with resulting adverse
effects on seo. Do not use redirects unless there is a clear reason for doing so.
2.3.6 Hidden text, a deceptive seo method
The last two issues are not really mistakes but deliberate attempts to deceive search
engines using illicit seo methods. Hidden text (when the text color coincides with the
background color, for example) allows site owners to cram a page with their desired
keywords without affecting page logic or visual layout. Such text is invisible to human
visitors but will be seen by search robots. The use of such deceptive optimization
methods may result in banning of the site. It could be excluded from the index (database)
of the search engine.
2.3.7 One-pixel links, seo deception
This is another deceptive seo technique. Search engines consider the use of tiny, almost
invisible, graphic image links just one pixel wide and high as an attempt at deception,
which may lead to a site ban.