Thank you Ron Rennick for the response...
Contacted hosting support & they restarted the webserver... But still the issue remains...
See these domains:
http://www.lifestyleshacked.com/ in which WP for multi site is installed... It's working good & it is installed in the root via Softaculous keeping the 'In Directory' section blank(I say this because the hosting people suggested to install wp such a way in the root directory as they can't find wp installed in the root)...
http://www.adsupon.com/ Detached this domain from the multisite said above(first it was there)... Installed WP(single site as add on domain in the same hosting) in it & so now it's independent... That also working...
But when a new site is added, say http://grandmascookery.com/ into the multisite, the issue arises(you can see that)... As you know when we adding a new site to the multisite network, we won't install WP separately in that also... just doing it from the dashboard by parking the domain & following the steps of domain mapping plugin... Right...?
Then how this issue can be fixed...?
Thank you...