A site analysis tool told me about my site,
Search engines may think www.izap.in and izap.in are two different sites.You should set up a permanent redirect (technically called a "301 redirect") between these sites. Once you do that, you will get full search engine credit for your work on these sites.
how can i fix this bug ?

It is not a "bug"

use

Options +FollowSymlinks
RewriteEngine on
rewritecond %{http_host} ^domain.com [nc]
rewriterule ^(.*)$ http://www.domain.com/$1 [r=301,nc]

In your .htaccess as your site is hosted on Apache