I'm having this problem with my recently installed Windows/apache2/php server. When I load a page the text comes fast and almost instantly, but the images on the page take a while to start loading and there is a lag between the load of a group of images and another. My site is www.hlspain.com and www.hl2spain.com, you can see it for yourself.
It might have something to do with keepalive and number of connections, but I think I got it well configured:
You may want to play around with mod_expires to add cache headers your images, .css and .js files . The loading time of your first page will not change, but subsequent pages which reuse the same files will be much faster.
If you don't add the cache headers, you're browser will have to guess if it can cache the file or not, and it may spend a little time checking with the http server to see if the graphics has changed. After adding the headers, your browser won't even check to see if the graphics has changed, it just assumes that the cache copy is up to date untill the expiry time (which you can set with mod_expires).
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