Hey I have 1 question that is I have created 1 site and that is giving an error "This site is harmful"..
so what can i do?
You'll need to give us more information than that, if you want us to help you.
How long has your site been online? When did the message first appear? Where are you seeing this message? e.g. From your browser, in Google Webmaster Tools, in search results or where? Is that the whole message?
You should check your site for any files that don't belong there, or any alterations to your files. Repair any damage you find and run a virus scan on the site. Change all your passwords and make sure you use only strong passwords.
Also run anti-virus and anti-malware scans on any computer you use for development of the site.
Change all passwords that you use to access the site.
Are all apps (and any of their plugins) up-to-date?
this means simple you site was hacked and distributing malware or some sort of back end function which will be will noticed by Google and other set of Browsers.
All you have to do is run a website scanning, if it infected by malware means you have to remove and make necessary security changes and submit an request in Google webmaster tools or stopbadware site. they will review your site in 1 -2 days and removes the warning!!