reach : The degree to which a Web site reaches customers. Measures of reach include overall traffic volumes, number of visits, number of new visitors, ratio of new to returning visitors, and visitor geographic data. Reach metrics depend on information from various sources.

Really Simple Syndication (RSS) : A method of distributing links to new content in a Web site; the recipients are people who’ve subscribed to the RSS feed for that site.

reciprocal links : An exchanging of links where two sites link to each other: site A to site B and site B to site A. This is essentially a barter and generally does not contribute much, if anything, to link equity, but it is not harmful.

redirect : An HTML command that automatically forwards incoming links to a different Web page.

relative link : A link that references a file located in a physical directory relative to the current page or the root of all directories, so it can simply start with the page name and leave off the http:// and domain information.

response metric : An element that visitors are responding to on a Web site, such as an image, a newsletter, or an e-mail.

response time : How fast a Web server is and how long it takes for users to load a page from that server.

retention: A measure of how many customers remain once they come to a Web site.

reverse DNS lookup : Looking at what Web server a user is coming from.

rich media : Content that enhances a Web page, such as images, video, and audio.

ROI : An acronym for Return On Investment.

RSS : An acronym for Really Simple Syndication.

RSS subscriptions : News feeds that automatically show updates to a Web site that offers RSS content.