Invitations to a special event in Toronto, skedded Jan. 31, went into the regular mail yesterday, and will bombard email in-boxes on Monday. Yahoo Canada will now rank search-engine ads using a new formula based on the amount advertisers pay for key words and the relevance of each ad.

The advantage for marketers? The ability to build campaigns with multiple ads linked to multiple key words, and to target by geography. The new search engine has already been unveiled in the US, and beta tests were previously conducted in Scandinavia and the UK.