Why there is a strong trend to use m.* (mobile) sub-domain for non desktop devices instead of using CSS rules to adjust the look of a website?

Question

There is a wide range of web capable devices that require different display adjustments, not only mobile phones. Maybe I'm wrong but I think that the m. sub-domain will be the same burden as WWW or http: or :80.

CSS enables us to ensure a proper display in all media, so why are so many publishers and evangelists promoting creating mobile sub-domains?

Answer 1

With CSS you can control the presentation of the document, not the document iself.

A user surfing the web with a small device screen may not be interested in reading tons of lines of text, but only useful informations.

A website made for desktop users usually contain lot of html code, scripts, images and other resources the browser has to download. A user using a handheld device may find it too slow to load, or consume too much bandwidth, or the JS code may be sloppy and make the site virtually impossible to navigate.

Also many external loaded resources won't be cached by many handheld devices until their size is really lightweight.

Answer 2

m.* domain do not only change the graphical style of the original website. Here's what I've seen:

• lazy content loading for lowering bandwith (ex: gmail which display only a few mails)
• less widgets (ex: chat, applications in Facebook mobile site [not the application])
• different interactions (touch, I know there is a touch version of facebook, besides the mobile basic one)

there must be many other changes.