You can tell if a website is secure (and therefore safe to use a credit card) by checking for the https protocol in the URL and for the "Lock" icon on the browser. The icon will have specific information about the website and it's level of security. You can read more about identifying secure websites at this article in our Knowledge Base: http://info.ssl.com/article.aspx?id=10068
As for the legitimacy of the business, you would be best to check with the Better Business Bureau.
As for the legitimacy of the business, you would be best to check with the Better Business Bureau.