need help with sed

[Guillaume <guillaume chardin gmail com>]

Hi,

When I run this command:
     echo  2008:04:23 | sed 's/://'
The result is
     200804:23

I expect to have this :
     20080423

What is wrong with my very simple regexp  ':' why all occurence of the
char ':' are not deleted ?

its make me crazy, can someone help me ?

Thanks
-- 
Guillaume