1. A method for content analysis of a text, the analysis depending on a presence of a plurality of keywords in the text, the method comprising: A) providing an incidence database including at least a first counter and a second counter, said first counter for indicating an incidence of a first keyword of the plurality of keywords, said second counter for indicating an incidence of a second keyword of the plurality of keywords; B) supplying a detection tree including a plurality of branches, each branch of said plurality of branches matching a string of characters, and said detection tree also including a plurality of sites on said plurality of branches, each site associated with a keyword of the plurality of keywords; said plurality of sites including a first site associated with said first keyword and a second site associated with said second keyword; C) reading at least one character from the text D) selecting from said plurality of branches, a current branch matching said at least one character; E) reading at least one more character from the text; F) selecting a sub-branch of said current branch, said sub-branch of said current branch matching said at least one more character; G) reaching said first site H) incrementing said first counter upon said reaching said first site; I) updating a score upon said incrementing, said updating being dependent on a condition, said condition including a limitation on a value of said first counter and said condition also including a limitation on a value of said second counter.