Internet Explorer handles AJAX responses different than other browsers. It will cache the response. The tendency on most articles I’ve read is: Caching is bad and you need disable caching!. No!!! Although Microsoft didn’t program Internet Explorer to respond according to RFC IE should do, that’s not an excuse to totally disable Cache. When visitors click on a link they expect something happens. Although AJAX makes the response time shrink, you don’t have any guarantee about the novelty of the content.

Sending the right headers

No, I am not talking about soccer. WordPress sends headers to prevent caching. I changed that because caching is not that bad. It’s all about sending the right headers and extending the intelligence in WordPress. The WordPress database keeps track of all date and times when the content changed. This is great, because now you can incorporate that date and time into the header. The second time the user asks for the content, the client send a If-modified-since in the request header with the date and time of the first response of the same content. If the content isn’t changed since, the response will be a HTTP 304 Not Modified (nothing more), the client will than get it out of the memory or the temporary Internet files.

Typically this saves a lot of bandwidth and latency.

Prefetching

The JavaScript on the client side tries to guess if you go to click on a link or not, just by measuring the time your mouse cursor is on the link, if it’s more than 0.2 seconds, it evaluates that chances are that you are eventually clicking on the link are big. So JavaScript starts fetching the page into memory.

In combination with the paragraph above, this gives a great performance boost. If the user doesn’t click on the link for now, it doesn’t matter because the next time the user might click on it, and on that point the JavaScript only have to collect a HTTP 304 Not Modified header (which is lesser than 300 bytes).

I first looked of course at the Gianni Milanesi’s AjaxWP. This looks promising if you like some DHTML in combination with Ajax. It’s also easy to setup… so what’s the problem? Well, it’s using Prototype, Scriptaculous and a history library. Which are all fine JavaScript libraries but do not improve load time. In fact, according to www.websiteoptimization.com it takes about one minute on a 33k6 telephone line on its first visit to completely load the site (without browser rendering). The Bloxpress 2 is a very fine WordPress theme, with a high coolaid level. But again, the load time is nothing to be proud of. And it’s a theme, I wanted my own the Brajeshwar theme to have Ajax.

I personally don’t like libraries, because you either use you nasty hacks because they don’t do what you want, or they just are far to big, which then you have a problem with legacy clients (which the processor can’t cope) or dialup users, which are very grateful that they could actually use your site within a minute

Because I want to use Ajax to improve the download and render time of the site instead of making it worse by implementing those libraries, I decided to write my own implementation.