Why are google maps displayed incorrectly?

Why doesn't google link to images.google.com in it's navbar?

• http://news.google.com, http://maps.google.com, http://docs.google.com all use the subdomain to display contents and are displayed as such in the navbar in google homepage. I expected http://images.google.com to be used as link but the one mentioned is http://www.google.com/imghp? Anyone knows why the subdomain isn't used directly? Also what does imghp stand for?

• Answer:

  The short answer is that it is faster. Each subdomain of a domain could point to a different server, so they require a separate DNS lookup the first time that they are used within a certain amount of time (roughly speaking). The majority of traffic to the Google Images homepage comes from clicking the "Images" link from the Google homepage or one of the Google search results pages. The subdomain of the Google homepage and the search results page is "www," so any users on one of those pages will already have the DNS lookup cached for "www." However, they likely do not have the DNS lookup for the "images" subdomain. If the link pointed to "http://images.google.com" it would likely take an extra 25-200ms to load for most users. This link used to point to "http://images.google.com," but we changed it when we realized how common it was for people to get to the images homepage from one of the web search pages. Given how google treats subdomains, they could also move maps and news to the "www" subdomain, but these domains are more frequently typed in directly, so the speed increase would not be as significant. "imghp" stands for Images Homepage.