Hi
thanks Ida..
Based on your inputs.. I have tested on another Mac system with below configuration.. All is good. I can open Office web apps in that Mac.
Configuration:
Mac OS Version: 10.6.8
Safari : 5.1.9 (6534.59.8)
chrome: 28.0.1500
Everything opened in chrome but it always warns below error in this systems two.
warning message : "Could not load SharePoint browser plug-in"
I could not figure out why it is failing in the mac which got most latest Mac OS 10.8 and safari 6.0.2.