There's been quite a lot of discussion online (and a little offline) about a recent blog article called:
How I Sped Up My Site 68.35% With One Line of Code
I think the biggest buzz about this article has been in the SEO community, who suddenly got all excited about a magical way to speed up web pages. Mentioned by Moz (the organic optimisation industry's catnip) you could be fooled into thinking that one person had suddenly found a way to massively boost a site to the top of the results pages.
Note: For those who don't know, the speed a page downloads is cited as one of the numerous factors taken into consideration when search engines such as Google rank (judge) your site... having a much faster page load speed with just one little line of code would be fabulous.
But alas, that's not the case.
You see, I think this article is misleading as it explains how to use an HTML tag called "rel-prerender".
For those who don't know, the rel-prerender tag is used on a website to place into computer memory the next page the site developer expects the users to click on. For example, Google sometimes use it in their search engine results pages (SERPs) to make the experience of clicking on the first result much quicker.
To explain how this works on your own website, let's imagine you are on page 1 and want to automatically call-up page 2 behind the scenes (so that it appears very quickly). You therefore insert the "rel-prerender" tag in page 1 to call up page 2 before it is clicked on.
Where might you use this?
Well you might us it on a login-page (page 1) where the logged-in page (page 2) is usually the next step. You can even use it in an eCommerce site to pre-render the shopping cart I guess.... BTW: DO NOT DO THIS!
But as you would expect, there's a catch. Pre-rendering page 2 is the act of requesting a view of it in advance. So people arriving on page 1 can trigger a page 2 view without ever seeing it and in many cases they won't. This means that in some analytic packages this is recorded as a page impression (not in GA, it's clever like that) and ads on that page may be triggered even when nobody's there to see them. Plus it also adds load onto your servers whenever a page is requested, so don't tell your tech support person you're adding further load onto the system that may never be used.
So does it have an effect on SEO? Well I may be wrong.... but I really can't see how it helps organic site optimisation as you are not speeding up the render of the page you want to appear in the SERPs (Page 1). What you are actually doing is speeding up the potential delivery of the next page (page 2) you expect the user to see. And that's not SEO, that's a caching strategy.