A Keyword Set allows to define many web pages based on their HTML content. This feature is very useful in the Website Filters.
A Keyword set can consist of an unlimited number of elements. When defining these elements, you must use just words and phrases. Masks are not supported here because, anyway, a word or phrase will be searched as a part of the whole page HTML code. As a result of this search system defines whether a website filtering rule is applicable or not.