There are some mobiles that will only show a limited set of these tags.
If the text appears normal your browser does not support that tag

Text formatting
[br] line break
Text styles
[b] Bold text [/b]
[i] Italic text [/i]
[u] Underlined text [/u]
key: n=number h=hex digit
Desktops can use any text size.
Many mobiles only use at best 2-3 font sizes.
[size=nn] 22px text [/size]
Colors can be used in 3 or 6 digit hex with or without # symbol.
Do NOT use newlines in colored or sized text use the [br] line break tag.
[color=#hhhhhh] Colored text [/color]
Links and images
http:// addresses are automatically converted to links.
[url]http://site.com[url] does the same.
[url=http://site.com]some text[/url] Creates a text link to the address.
[img]http://site.com/image file name[/img] will show an image.
[img] tags can be nested in [url=http://site.com] tags to produce image links.
Most BBcodes can be nested
if using [url] tags
they should be the outer BBcode tags.
[url=http://xtgem.com/feed][b][i][size=18][color=#0ff]
a link in bold italic 18px red
[/color][/size][/i][/b][/url]
email addresses
[email]your@mail.com[/email] .
Creates a mailto: link on supported devices.
Show html
[code]...[/code] tags are used to show html and other codes or scripts

<script type="text/javascript>
alert("hello world");
</script>

Other codes
(c)=© (r)=® (tm)=™
Html entities can be used in the numeric format
ie: @ = @