Apple recently added their Safari web browser to the Apple Software Update and pre-checked the box by default. This effectively means that a lot of Windows users will now, possibly without knowing it, have installed Safari.
I'm not going to discuss the ethics of this practice here, instead read John's Blog - CEO of Mozilla.
But what it means for the humble web designer or developer is that we should really be installing Safari on our Windows machines and adding it to the list of browsers we test our sites against as the number of users is bound to increase as a consequence.
Competition in the browser business is good and over the last few years Firefox has begun to gain ground on Microsoft's Internet Explorer domination. It has also forced the browsers to become more standards compliant, thereby helping web developers and designers design cross-browser, cross-platform web pages.
According to Apple, Safari is a standards compliant browser built on the open source WebKit project, so hopefully if your pages have been built to W3C standards they will require minimal checking, but it is always wise to test. Apple have a range of web developer resources for the Safari browser, including the Safari CSS support, Safari developer FAQ, and a general web development best practices guide.