make a phone call on mobile using native html (no javascript needed)

simply an <a> tag:
using "tel:" protocol in the href like other protocols such as "email:", "javascript:"
<a href="tel:xxxxxxxx" >phone me</a>

if country code is needed, start with "+" and your country code,
the country in Hong kong is 852 so:
<a href="tel:+85218503">call HK Observatory</a>

example:
call 萬寧妹妹

the code were tested with the following devices using its default browser:
Galaxy S2(Android 4.0.4),
iphone 4S(IOS 5.0.1),
WinPhone 8

hope the information above can help u all