Hi, my site was running with index.asp as home page and now I have changed the home page to index.htm. by this site is not in google search with any keyword.
As you had changed the site address it will take time. One question Is you site Indexed with .htm extension?
I would recommend you checking to see any 404 error via Google Webmaster Tools if you already got your website being verified. Otherwise I would recommend you do 301 redirect the old one to your new .htm page helping Googlebots found your new page much easier. This could also help preventing 404 error for your new homepage as well.
It takes two weeks or more but less than a month to see your changes!! Look at your history page in google
your site will be still accessible typing the main domain so changing the index file extension would not make the site go dead. the reason you are not finding your site on search result is because you must not have done the 301 redirection from asp to htm. 301 redirection is known to maintain the ranking as this is permanent redirection telling the search engine bot that your previous content page moved to the new page. setup 301 redirection and build some backlinks so that google finds your site under new index file and knows that your old file has been redirected