Let's say we have this link in an HTML document:

<a href="http://www.google.com/">Google</a>

This selector works - returns 1 element:

$("a[href^='http://www']")

This selector does NOT work in 1.3b1 because it contains a dot "." in the attribute filter value - returns no element:

$("a[href^='http://www.google']")

The same thing occurs for all attribute filters: ^= and *= and $= and =.

There must be a problem with a regular expression in Sizzle.