Some search engines consider both the frequency and the positioning of keywords to determine relevancy, reasoning that if your keywords ultrasonic clamp on appear early in the document, or in the headers, this increases the likelihood that the document is on target. For example, one method is to rank hits according to how many times your keywords appear and in which fields they appear (i.e., in headers, titles or plain text). Another method is to determine which documents are most frequently linked to other documents on the Web. The reasoning here is that if other folks consider certain pages important, you should, too.
