1. A method for extracting web information, comprising: selecting a number of Hypertext Markup Language, HTML, tags as tag ruler elements to generate a tag ruler from an HTML text of a web page according to sequence of the HTML text; matching the HTML text with the tag ruler elements in the tag ruler according to the sequence of the tag ruler elements in the tag ruler, segmenting web information according to matched HTML tags, and saving web information segments and location information of HTML tags enclosing the web information segments in the HTML text; and extracting web information needed by a user from the saved web information segments according to an information extraction matrix configured by the user and vector multiplication rules; wherein the information extraction matrix is configured by the user according to the web information needed by the user, and the information extraction matrix indicates location information of HTML tags enclosing the web information needed by the user in the HTML text; wherein the information extraction matrix comprises three columns; one column of data indicates a field in a row of the table from which the web information needed by the user is extracted; another column of data indicates which information field tags enclosed in a pair of <TD></TD> in the HTML text are the HTML tags enclosing the web information; and the other column of data indicates storage location of every extracted web information field in a database.