As I dug deeper into the enigma of page load times and how that effected SEO (a fun tidbit, slow pages get bumped down in Google Searches) I stumbled upon DNS prefetching. No, this is not a dog thing. Rather it is actually a nice little tag that suggests to the browser that they should look up a domain as soon as it is convenient. So instead of doing the lookup for each image that the browser requests it does one lookup and loads the image. Thus increasing your page load speed. Booyah!
As a good example, this site uses two locations for fonts and sharing tools (Google Fonts and ShareThis). Both of these URLs are somewhere else, not here, and thus when the request is made the browser stops and does a lookup for the domain. Since this can slow the page load this nifty little tag requests the browser to lookup before are even requested. Ideally, you don’t need to do this for all your domains, but I generally use it for the ones that I hit frequently or will be getting a lot of requests.
<link rel="dns-prefetch" href="//fonts.googleapis.com" /> <link rel="dns-prefetch" href="//w.sharethis.com" />
Any questions? I definitely am interested in carrying this conversation further since I haven’t seen whole lot of drawbacks to doing this other than the amount of DNS prefetches that you can do.