It's more usual to give good examples and best practices, but since I'm visiting and analyzing .mobi websites, and I have seen so many bad things, I decided take the snake by the tail. Feel free to avoid these worst practices.
- At the head of the hall of shame, I claim … the 'infinite loop', (e.g. b0x.mobi, and auditpro.mobi) which redirects you to it self as long as you'll fancy it. I hope at least people using it do it consciously and are not expecting too many visits.
- Long domain names. Oh yeah, that's something every site builder always dreams of: to tell his colleague that he owns a bigger domain than him! But except for making a good geek joke, it's totally useless. Especially when the user will have to press an average of 1.6 key per letter, and all with one thumb! Don't even ask the user to remember the domain name, he's as lazy as the developer. Best examples: 141592653589793238462643383279502884197169399375105820974944592.mobi (maybe an encrypted secret message!) or arthurfrommerstravelessentialsclothingandgearforallbudgets.mobi even canneslionsinternationaladvertisingfestival.mobi .
- Using Microsoft IIS server content-type adaptation. And maybe it's the default IIS configuration (or due to .NET?). I saw this behavior on lots of .mobi domains hosted by IIS (v4, 5 or 6). If the User-Agent is detected as mobile (at least most of the Nokia ones), IIS will send back a wml content-type. Oh nice and clever, but the content it self is still the same, a proper XHTML-MP page, it's not adapting itself into some wml code. So ultimately it's tricky and confusing, and completely pointless. Example: myspace.mobi .
- Provide a PC page as the default page. It's fair if you want to have PC and mobile version of your site on your .mobi domain, and put a link to 'PC version' or 'mobile version' (or better: UA detection). But please, the default page must be least common denominator! So go for the mobile version. Don't worry, easy to remember, just think of the TLD significance. A nice example: bahamasvacations.mobi, you’ll have to load 266KB on your phone just to reach a link to the real mobile version.
- Do two or more redirections before reaching the front page. Some websites redirect you (transparently using HTTP protocol) one time to go from mysite.mobi to mysite.mobi/home, and one more time to mysite.mobi/home/new-index.php (or even mysite.com and some others hops). Whatever the reason is, it's bad. Because it means 2 or 3 more phone-server trips, and so increases waiting time for the (always impatient) user, not to mention the cost of the additional data. Remember that the response time (reactivity) of mobiles phone are not as fast as on pc. If you need to redirect the user from the front page to another, it's better to use URL rewrite rules. Example: nba.mobi, 3 redirections.
PS: For all of the quoted domains, thank you for giving me examples for my article, and don’t take offence to have been quoted.