By default what DSCP values are used when initiating HTTP traffic? If I wanted to match HTTP traffic to a DSCP value, what should it be?
Default QoS Markings are "Best Effort" (AKA "0")
Also, QoS needs to be honoured at each Hop, so it's mainly useless on the Internet (Most ISPs strip/remark to 0, or do nothing more with it)
Even if you managed to PAY for a better QoS handling, it would stop at your ISP's Peers borders.
Now, if you're talking for within your own lan, there are many ways to mark the traffic, depending on platform & topology, but each hop must be configured for it. This means configuring each devices to classify/prioritize/process each type of traffic you have, the way you want it to be done.