What is CSS Rules To Hide Elements?
Definition
CSS Rules to hide elements are used in case when ads are not delivered via HTTPS requests.
Meaning explained
CSS rules hiding elements is one of the possible adblock countermeasure strategies.
In case ads are not delivered by HTTPS requests but through an in-house ad server, adblock software checks for specific CSS elements that deliver ads. Adblock then appends a rule not to display the element to CSS stylesheet before sending it to a browser for page rendering. In effect, the particular CSS containing an ad is never made visible.
Other countermeasure strategies might be: