Cloaking refers to any of several means to serve a page to the search-engine spider that is different from that seen by human users. It can be an attempt to mislead search engines regarding the content on a particular web site. Cloaking, however, can also be used to ethically increase accessibility of a site to users with disabilities or provide human users with content that search engines aren't able to process or parse. It is also used to deliver content based on a user's location; Google itself uses IP delivery, a form of cloaking, to deliver results. Another form of cloaking is code swapping, i.e., optimizing a page for top ranking and then swapping another page in its place once a top ranking is achieved.