Yes, your website is secure. Your visitors are using an old version of Web Browser/Operating System combination and should either upgrade their Operating System or dowload a safe browser for their current computer.

This article presents a list of safe modern browsers that should be used on users' Operating Systems. All these browsers and OS combinations guarantee a secure web browsing experience, as of November 2013.

Safe Browsers for MAC OS X

Safari 3.0 and above
Opera 8.0 and above
Chrome 5.0 and above
FireFox 2 and above 

Safe Browsers for Windows Vista, Windows 7, Windows 8, and greater

Internet Explorer 7 and above
FireFox 2.0 and above
Opera 8.0 and above
Safari 3.0 and above

Safe Browsers for Windows XP

Chrome 6.0 and above
FireFox 2.0  and above
Opera 8.0 and above

Unsafe Browsers for Windows XP

Internet Explorer
Recommended Action: download Google Chrome or FireFox for Windows XP

So. why are there safe browsers and unsafe browsers?

It all boils down to something called SNI, short for Server Name Indication, which is something older computers such as Windows XP and Android 2.x do not provide support for.

SNI allows multiple SSL-enabled websites (online stores, for example) to be hosted on a single shared IP address, which saves on costs. IP addresses are in short supply: there are fewer IP addresses than there are websites. The math is simple: if we want the web to keep expanding, we have to host multiple websites on single IP addresses and reduce our IP address footprint.