How do I fix "Safari Can’t Open the Page" error onOS X Snow Leopard 10.6.3.?

Try opening a different page.

If Safari doesn't open a page or work as expected on your Mac - Apple Support

Be advised most web pages will no longer load with Snow Leopard's version of Safari, because it cannot decrypt the security layer incorporated in them for about a decade and a half now.

The reason Safari can't open that page is that it cannot establish a secure connection to the server. That Mac's version of Safari predates recent SSL and TLS versions that have been incorporated in nearly all websites for at least a decade.

TLS security - Apple Support

Digital certificates and encrypted websites in Safari on Mac - Apple Support

The bottom line is that you can't fix it. Only a website developer can choose to forego commonly accepted security protocols, at the risk of losing clients demanding them. Not all website developers are motivated to incorporate the latest security protocols, but none that have are likely to go backwards.

Does that Mac even have an Internet connection?

Connect your Mac to the internet - Apple Support

What is the exact wording of that "Safari can’t open the page" message?