Following numerous security (1,2) concerns regarding Safari 3 on Windows, Apple has released an update to Safari fixing these issues.
Safari 3.0.1 is available in the Apple Software Update as well as on the Apple website.
Macworld offers the following in regard to what the update fixes;
The security improvements in Safari Beta 3.0.1 include correction for a "command injection vulnerability," corrected with additional processing and validation of URLs that could otherwise lead to an unexpected termination of the browser; an out-of-bounds memory read issue; and a race condition that can allow cross-site scripting using a JavaScript exploit