Matt Cutts is back to answer questions regarding search engine optimization and related topics. In this video, he responds to a query by Linda from New Jersey. She wrote in to ask whether cross linking 3 of her websites would have any adverse side effects.
Since PageRank is largely determined by the quality and quantity of inbound links, it is tempting for those who own several sites to cross-link among their web properties to boost their rankings. Matt says that this is fine if each of these are somewhat related. For instance, if all of them sell clothes but one caters to men, another to women, and the last to children.
However, if the sites have nothing to do with each other then there might be some problems. Visitors and competitors might find it odd when a site about insurance links out to a blog about fashion accessories, which in turn links to a mobile review site. For a small number of cross-links, the practice might not be very detrimental, but when the figure escalates into the dozens or even the hundreds, then cross linking starts becoming unhealthy. Rather than attracting more visitors, people will probably be turned off after seeing so many irrelevant links on the page.