VBScript is peculiar to Internet Explorer and is deprecated by Microsoft. It's not supported by any other browser. Microsoft itself is ending support for VBScript in IE, and IE8 will only handle it in compatibility mode. Future versions of IE will likely drop support for it altogether.
There's not much you can do short of run a Virtual Machine with IE (you'll want XP or Vista with IE7 if you want to make sure the VBScript will operate; you also need to make sure that the user *doesn't upgrade IE*).
You will also want to contact the administrator for the website to inform them of the problem as they will need to recode parts of their site to be compatible with future browsers.
Safari, Chrome, and Firefox aim to be compliant with published web standards. They do have some some browser-specific features, but all encourage you to not use them except in extenuating circumstances. Some web-sites use non-standard Microsoft-specifc and Windows-specific technologies because of how common their browsers are, and because their browsers tend not to implement published web standards very well.
In the industry, FireFox compatibility is really the gold standard. As a browser, it's universally available, and it explicitly aims to implement standards as published. Sites that are not compatible with FireFox are arguably not web-sites at all.