Hidden text – SEO WIKI
Hidden text is one of the black ways of SEO optimization and promotion, consisting in the fact that the page creates text that is not visible to users, but visible to search robots. To mask texts on a page, several methods are used:
Make the text font color the same as the background color;
Set the font size to zero;
Overlay the image on top of the text;
Hide text using commands in CSS.
Hidden texts are intended for search engines, so they contain to the maximum the keywords and phrases necessary to search for this page. However, this method has long been known to search engines, and in most cases it does not work. If robots notice an attempt to deceive users on the pages, then not only a separate page, but the entire site may fall under the ban.