3. A computer implemented method as in claim 2 wherein computing the frequency with which a keyword appears in conjunction with another keyword in at least a portion of the plurality of web-based user profiles further includes: computing the degree to which the two keywords tend to occur together; determining a ratio indicating the frequency with which the two keywords appear together; and determining a correlation index indicating the likelihood that users interested in one of the keywords will be interested in the other keyword, as compared to an average profile.
3. A computer implemented method as in claim 2 wherein computing the frequency with which a keyword appears in conjunction with another keyword in at least a portion of the plurality of web-based user profiles further includes: computing the degree to which the two keywords tend to occur together; determining a ratio indicating the frequency with which the two keywords appear together; and determining a correlation index indicating the likelihood that users interested in one of the keywords will be interested in the other keyword, as compared to an average profile. 4. A computer implemented method as in claim 3 further including processing the computed degree, the determined ratio and the correlation index to determine a percentage of co-occurrence for each keyword.