lucy24 - 2:28 am on Aug 31, 2012 (gmt 0)

The big drawback to js here is that it can only execute after the page has loaded. So you get your user with a weeny cell phone on a sluggish connection first waiting for the "real" page to load up, and then they have to wait all over again for the cell-phone version.

There are 3rd party websites that provide a JS that uses their proprietary system, but that scares me because they may or may not be accurate, or even around in a few years/months/days.

Are you looking at routines that are called from within your site, but live somewhere else? Worse and worse, because now you've got even more stuff for the user to wait for.

You want something that gets the necessary information before it starts building the page. Or, at worst, before anything but the html has loaded.

:: detour to investigate ::

<ot>
If anyone doubts that g### really uses those "author" tags to generate search results complete with pictures of the author, try the search query I just used. One page, 30 results, 5 white men.
</ot>

Awright, folks, what are we missing here? I'm seeing:

A) responsive site that adapts more-or-less fluidly to the UA that called it up

B) javascript that detects viewport size and/or UA and replaces originally loaded page with alternative version

C) proprietary gimmicks that serve up different page versions and/or different sizes of images based on javascript function called after html (at a minimum) has loaded up

D) php or server file (htaccess etc) that detects UA by name and routes user to appropriate page, and/or builds appropriate page on the fly-- but only if UA is a known quantity, because most UA names do not include viewport size

You're looking for Option E) aren't you?