As pointed out by CultofMac, Apple has just pulled Messages for Mac beta ahead of OS X Mountain Lion launch. This means that if you haven’t already installed it on your Mac, you will now have to wait until OS X Mountain Lion is officially released next month to get your hands on it. Apple introduced the Messages for Mac beta back in February as part of initial Mountain Lion preview.
According to the source:
“It’s unclear when or indeed why Apple removed the Messages beta from its site. I had an issue with the application late last night, and I decided to uninstall the application and then install it again to see if this solved the problem. However, the Messages for Mac beta page has been removed from Apple’s site, and when visiting the URL, you are redirected to the OS X page.
There’s still a Messages for Mac link at the bottom of Apple’s Downloads page — as you can see below — but again, it just redirects to the Mac OS X page, where a Messages beta cannot be found.”
So those who already have Messages beta installed on OS X, we recommend holding onto it for the next few weeks.