1. A computer readable storage medium having stored therein a keyword output program causing a computer to execute a keyword output method comprising: receiving a target keyword from a predetermined input unit; extracting, from a keyword storage unit that stores a plurality of keywords in association with each other according to degrees of relation among each other, a plurality of related keywords that have degrees of relation equal to or greater than a predetermined degree of relation with respect to the target keyword received, the stored plurality of keywords having been used for a search at a search site for searching contents; reading evaluation expressions corresponding to the target keyword and the plurality of related keywords from an evaluation expression storage unit that stores evaluation expressions correspondingly with each of the plurality of keywords stored in the keyword storage unit, each evaluation expression having been extracted from a content containing the corresponding keyword, and calculating for each of the plurality of related keywords a commonness degree between the evaluation expressions corresponding to the related keyword and the evaluation expressions corresponding to the target keyword; calculating for each of the plurality of related keywords a degree of association between the related keyword and the target keyword by using a distance derived from the keyword storage unit for each of the plurality of related keywords with respect to the target keyword and the commonness degree of the evaluation expressions calculated for each of the plurality of related keywords; determining whether the degree of association calculated is greater than a predetermined degree of association and extracting a first related keyword having a degree of association greater than the predetermined degree of association from among the plurality of related keywords; and outputting a keyword layout drawing including the target keyword and the plurality of related keywords arranged according to the degrees of association between each other through a predetermined output unit such that the the first related keyword is displayed distinguishably from other related keyword.