Is .co extension good for a global domain ? I am thinking of buying a domain and i am confused, because the domain i want is available for .co but not for .com. Please guide because i know .com is best TLD but can .co compete with it ?
No, .co is a poor substitute. .com is still king, and if you want to be taken seriously, that is the best extension to use.
if your are making something brandable, where your domain name is your brand then you can go for any extension as long as people can easily remember it. Browse http://www.go.co for the showcase of top .co websites and find out the how they are being branded.
.CO is mainly for Columbia country website with target Columbia visitors. It not good to register with and target the global . As Matt Cutt mention that Google will assume you are target Columbia or specific website from Columbia. It would be best to go with .net and .com rather than .co if you target global market.