4.2 Oddly flavored mobile browsers
One can wonder why, in a market where all recent cell phones support XHTML or a subset thereof, tag soup still prevails over structured and clean markup. The slow adoption of web standards as a tool for device independent design is probably related to what looks like a mobile browser war between Japan's mobile carriers. In the next few paragraphs, I point to some technical issues to give a better idea of the situation.
In 1999, NTT DoCoMo launched its revolutionary i-mode service,51 enabling mobile phone users to browse the web. It also introduced its own Compact HTML (cHTML) format,52 a lightweight subset of HTML 2.0, 3.2 and 4.0, with which i-mode websites could be created. Soon thereafter, cHTML underwent a name change and became i-mode compatible HTML or simply i-HTML.53 NTT DoCoMo extended the format several times, and with each new version, more proprietary tags and attributes were introduced. i-HTML 5.0 for instance, supports Internet Explorer's <marquee> tag and obscure attributes such as ilet, iswf, telbook and ijam, which all hook in on functionality only found on recent i-mode phones. That is not all though: NTT DoCoMo has also jumped on the XHTML/CSS train. Its i-XHTML54 is based on XHTML Mobile Profile (XHTML-MP),55 an XHTMLMOD application extending XHTML Basic with mobile-specific modules, which was proposed by the Open Mobile Alliance (OMA) (2001).56 However, as one could expect, NTT DoCoMo also added a proprietary flavor to its XHTML implementation; in order for i-XHTML 1.0 to be backward compatible with earlier i-mode specifications, it supports most of the proprietary tags and attributes found in i-HTML.57
As for Cascading Style Sheets, we see a similar situation. NTT DoCoMo handsets support i-CSS, which is a partial implementation of WAP CSS (2001),58 another specification backed by the Open Mobile Alliance. WAP CSS specifies a subset of CSS 2 and a number of mobile specific extensions. One of the limitations in i-CSS is that only inline styling is supported—external style sheets are not recognized.59
Another feature worth mentioning are emoji or pictorial characters. By inserting certain Unicode entities in the (X)HTML source, web developers can easily add icons and smilies to web pages.60 The downside however is that the emoji defined by NTT DoCoMo only work on i-mode phones—other browsers will display the entities as plain text or map another character to them.
51 More info about the i-mode service at http://www.nttdocomo.co.jp/english/p_s/i/.
52 More info about the cHTML format at http://www.w3.org/TR/1998/NOTE-compactHTML-19980209/. The document is only hosted as a “note” on the W3C site; the W3C does not endorse its content.
53 More info about i-HTML at http://www.nttdocomo.co.jp/english/p_s/i/tag/imodetag.html. Note the 8 different i-HTML versions: 1.0, 2.0, 3.0 (2x), 4.0 (2x), 5.0 (2x).
54 More info about i-XHTML at http://www.nttdocomo.co.jp/english/p_s/i/xhtml/imodetag.html. There are 2 different i-XHTML versions: 1.0 and 1.1.
55 The XHTML-MP specification can be found at http://www.openmobilealliance.org/tech/affiliates/wap/wap-277-xhtmlmp-20011029-a.pdf. Note that although this specification builds upon the W3C's XHTMLMOD framework, it is not a W3C recommendation as such. Furthermore, as some of the extra modules were not included in their entirety, XHTML-MP is actually not strictly XHTML Host Language Conforming as defined in XHTMLMOD.
56 The website of the Open Mobile Alliance can be found at http://www.openmobilealliance.org/.
57 An overview of the differences between i-HTML and i-XHTML can be found at http://www.nttdocomo.co.jp/english/p_s/i/xhtml/hikaku.html.
58 The WAP CSS specification can be found at http://www.wapforum.org/tech/documents/WAP-239-WCSS-20011026-a.pdf.
59 i-mode handsets can only render inline styling and a limited set of internal style rules (defined in the head section).
60 Emoji are mapped to certain code points in the so called Private Use Area of the Unicode standard. As there is no agreement between the major carriers about where to map which icon, their current implementations are completely incompatible.