Question: One of the requirements of one of my clients is to show a message to a user that's using an older version of Firefox, Chrome, IE or Safari. For the last two it's easy (IE 9+ and Safari 5+). But for Firefox and Chrome, the requirement is that the site supports the current and the previous version of each browser.
To get the clients browser and version is quite simple, but I need to know what is the last version of each browser. Is there any way of doing that?

Answer: 
Well, technically, all you need is a place that keeps track of what the latest version of each browser (Ideally with a web service).

A quick Googling I was able to find: <http://www.webdevelopersnotes.com/articles/latest-browser-versions.php>

It's not a web service, but you could simply parse that HTML and get the latest version of each browser. Alternatively, you could keep track yourself and manually update this information in your database.
The best I could find was [this](https://stackoverflow.com/a/9538555/1221382). It has an export option that allows to export in JSON, XML...