How can I know if my website is infected ?

There are various predominant characteristics which indicates you and also shows you the way and make clarity of yours though to understand that yours website is been hijacked or not and if it contains malicious code or hidden redirections.The following information extracted from Urlvoid . Urlvoid.com is a service developed by NoVirusThanks Company and started on 21 May 2010 that allows users to scan a website address with multiple scanning engines such as Google Diagnostic, McAfee SiteAdvisor, Norton SafeWeb, MyWOT to facilitate the detection of possible dangerous websites.

1) Your website takes longer to load web pages
2) Unknown popups or alerts messages are show up when you browse your website
3) When you visit your website you are redirected to other (unknown) websites
4) Antivirus alerts you when you browse your website
5) Your website is listed in scan reports present in our service
6) Users notify you they are redirected to other sites from your website
7) Users notify you they receive massive popups or security alerts in your website
8) You notice a drastic decrease of users that come from search engines
9) You notice unknown code (mostly javascript/iframes) in your website