Hidden text refers to the intentional hiding of keywords.
The use of hidden text has emerged in the course of search engine optimization. Its purpose is to place texts, keywords or phrases on a webpage. These need not be of the same content and the same topic and they are not visible to users. Previously, such text was read by the spiders when crawling and thus obtained a higher rank.
Text hiding is nowadays considered spam and violates Google’s Quality Guidelines, because it affects competition rights negatively. Recognition of hidden text can cause the websites to be removed from the search engines index and a penalty can be levied against it. Today hidden text can be easily recognized during crawling on the basis of increased keyword density and penalized correspondingly.
Hidden text is part of hidden content, which includes hiding keywords in links.
Text can be hidden in several ways. The font color can be made the same as the background or placed outside the margin. The font size can be set to 0 or the text placed behind an image. A further possibility is the use of CSS technology. Text is rendered invisible to the user using the formatting options “visibility:hidden” or “display:none.” Using CSS, it is also possible to separate layout and content and to relocate stylesheets in isolated files.