In Internet Explorer 8, the maximum number of concurrent connections to a host has been increased to 6.  However, the HTTP 1.1 Specification states there is a 2 connection limit:

"Clients that use persistent connections should limit the number of simultaneous connections that they maintain to a given server. A single-user client should not maintain more than 2 connections with any server or proxy"

So all browsers should limit connections to 2.  What's up with IE8??

According to Microsoft:

"The two-connection limit for HTTP 1.1 was due to a mandate that was established in the HTTP 1.1 specification (Request for Comment 2616) World Wide Web link. At the time the standard was first drafted (January 1997), the two-connection limit was appropriate, considering the dominance of narrowband Internet connections and the scarcity of broadband connections."

So I guess it is up to Microsoft to define "appropriate"?  Kinda funny how they can just throw away a specification and use the web protocols in a way they were not designed to be used.  I don't think it is up to Microsoft to decide how the web should operate.