Thanks great suggestion. I will create a custom 404 page for sure. I need your opinion on one more thing. First time when I've submitted sitemap of my site using Webmaster tools, i've got DNS error. Something like this
"Over the last 24 hours, Googlebot encountered 1 errors while attempting to retrieve DNS information for your site. The overall error rate for DNS queries for your site is 50.0%. You can see more details about these errors in Webmaster Tools."
So a per their recommendation i had words with customer care representative of my Web-Hosting provider. And he told me that there is something wrong with my htaccess file and asked me to delete it from the server. I did just what he suggested and now I'm not getting such errors. But still DNS status is showing something yellow colored warning sign, check the attached screenshot for more details. Is there still anything wrong?
My pages are indexed now.