What are the differences from a developer point of view between Safari for Mac and Safari for Windows?
I think it boils down to evaluate differences between (if I missed
I had an issue with the popup blocker in Safari in Windows XP. I guess the blocker didn't accept that the user clicked a link an Flash that then triggered a JavaScript that opened the Window. The did work in the other major browsers and Safari in OS X, though. Chrome also blocked my window in XP, but not in OS X or Ubuntu.
Font rendering can be different between Mac and Windows Safari as the systems typically have different fonts. As long as your page can gracefully handle missing fonts or different font sizes it should be fine.
Just wanted to add this experience I came across for Safari. Our devs are still going to look into this but not high priority for us since Windows Safari isn't much of our user base unlike Mac. But I think it relates to either (or both) - actual browser low level implementation of Safari by Apple, and/or javascript differences.
Our website recently implemented an HTML5 multiple file uploader. Single file uploads work fine on both versions of Safari. But when uploading multiple files, it fails on Windows. We had two different upload clients & endpoints for the uploader (think A/B testing flow), and one of them provided more details that may or may not point at the cause of the problem. On one of the client & endpoints, the client would send details of the filenames & filesizes of files to upload (as JSON array object) to the server endpoint (as seen via web inspector). On Mac where it worked, filesizes were valid, on Windows, they were 0 bytes.
I think the uploader is JQuery based or some other JS library. But I'm not the dev, so can't be sure. But I have a hunch this issue goes beyond JS libraries...
Style sheet rendering is significantly different between Safari and Windows. To see this, try creating a page that has an element with a z-index of -1. The windows version will function without issue, the Mac version will not allow you to select the elements. Trust me, I wasted about three hours trying to figure out by trial and error why a page would work in one system but not the other. The worst bit is that when Safari doesn't render something properly, it does so without any indication. You have to debug line for line, a dreadful experience.
A site I am working on now has a problem in safari for mac that isn't in safari 3 or 4 for windows. I cant figure it out for the life of me.