As I said ,the map displayed only on creating a new cshtml page with new css reference .
The above cshtml with the above big css does not work .However the new cshtml page with just the map div and reference to new small css (map.css) works fine.I am not sure what is the exact css problem.
But I think thats not a possibility because site.css starts with giving background image to the page and if I comment that line background image won't show up. So it is taking the background image surely from site.css
Below is the code for top most part of site.css.(The complete code for the file I had pasted few posts above ):