7. A keyword ranking determining method, comprising: using a computing device to perform the following: grouping data of a weblog according to a theme in a predefined set of themes, the theme being one of user groups included in the weblog, and the user groups being groups of users who selected a document using a keyword, wherein the document is a website, wherein the keyword is one entered by a user leading to selection of the document and included in the data of the weblog; storing the data of the weblog in a storage medium, the data of the weblog including information on the document, the keyword used in selecting the document, the user that entered the keyword used in selecting the document, and a selection number indicating a number of times the document is selected using the keyword; calculating a document concentration of the document corresponding to the theme using a relationship between a probability that the document corresponds to the theme and a probability that the document corresponds to all themes in the predefined set of themes, and applying a weight corresponding to the document concentration to the data of the weblog to adjust the selection number with respect to the document; generating at least one data set by grouping the data of the weblog applied with the weight according to a search intention, wherein determining the search intention involves grouping keywords used to select a same document as the same search intention, and/or by grouping keywords among which similarity is greater than or equal to a value as the same search intention, and determining rankings of the at least one data set according to the theme, thereby ranking the keywords in the at least one data set according to an associated user group, wherein the determining of rankings of the at least one data set comprises calculating a share of each of the at least one data set included in the theme using the selection number adjusted according to the weight, and determining rankings of the at least one data set with respect to the theme according to the calculated share; determining a main keyword representing each of the at least one data set from each of the at least one data set generated and ranked; and providing a set of ranked keywords for each of said user groups.
8. The keyword ranking determining method of claim 7 , wherein the share is calculated using a sum of the selection numbers in each data set and a sum of all selection numbers with respect to all of the at least one data set.