Recent browser have added an optimisation that enables the browser to resolve all the DNS names that appear inside a visited HTML page while the browser displays the HTML page. This can speed up the retrieval of the next link on which the user will click. Unfortunately, on websites that contain a large number of different hostnames on each page (e.g. pointers to homepages of users who have posted comments), this may lead to a large number of DNS requests for each HTML page retrieved. Some browsers even query for A and AAAA, a good sign of the growing importance of IPv6, but also a doubling of the number of DNS requests. Fortunately, websites may disable DNS prefetching by using some tags. Additional information may be found in http://www.pinkbike.com/news/DNS-Prefetching-implications.html