I was still able to install module using /Install/Install.aspx?mode=installresource but finally stuck when I was not able to add the installed module into page.
Finally, after reading several articles on web, I found web.config's httpRuntime element needs another attribute called : requestValidationMode="2.0"
I go the solution here (
And finally, I was on my way to regular work.
please note that I was trying this on having webmatrix installed and I was browsing the site in asp.net 4.0 integrated mode.Hope this will help to someone in the same kind of trouble.