1. A method for automatically validity checking a computer file defining content to determine whether the content complies with permitted design features stored in a profile specification, wherein the profile specification is defined by a plurality of page components having elements with attributes, and each attribute designates a rule indicating the permitted design features for that attribute, comprising the steps of: selecting an attribute from the file; detecting the features of the selected attribute; finding an attribute from the profile specification that matches the selected attribute from the file; comparing a rule to the matched attribute from the profile specification with the detected features of the selected attribute from the file; and, determining whether the matched attribute complies with the rule.