I have seen sites using tag to load images eg;
<link href='images.jpg' rel='somthing' type='something'>
Some people use this for image/css/page prefetching. You can read about it here.
Basically, once a page is finished loading the browser will see these
link tags and if the
rel attribute is "next" or "prefetch" then the browser will start downloading whatever the
href attribute points to and store it in the cache so that it will load very fast if the user clicks on it.
This method can be used to prefetch anything including images, style sheets, different web pages, etc. As long as the url used in the
<link> matches the url used to normally load the resource, it will load that resource from the cache.
For example, if your page had this link
<a href="page2.html">Page 2</a> and you wanted to prefetch it, you would add this to your page
<link rel="next" href="page2.html">.