httpd headers etc

I have been picking up knowledge of http headers, etc, as I've gone along - doing redirects, fopen(), fsockopen(), caching, etc, but I've not sat down and studied the http client-server exchange as a whole. So the time has come (the walrus said) to round out my knowledge. Reading the RFC(s) is likely to be a sonorous experience. Can someone recommend a readable article/tutorial which covers the ground to a reasonable depth? Please advise, =dn