Preloading, Connecting to Server, Timeouts.. There might be some who still remember this and yes, there even might be some still preferring this to HQ-Youtube and Livestreams. Those should take a closer look at this plugin: Firefox Throttle. This plugin allows you to throttle your speed while browsing & downloading in Firefox. Doesn’t make sense? Well, everyone who designed a Flash preloader once may be interested in this as it allows you to see your preloading-progress as shown with slower connections. I myself had to struggle often with self-designed preloaders as my internet-connection is top of the line so I probably don’t see my preloader at all. This plugin lets you change your internet-connection with one single click to, let’s say, DSL Lite. Et voilá – your preloader is preloading the content with 128kb/s instead of 1.8mb/s. Pretty cool at all and useful for HTML-Guys as well.

And finally you can tell your customer “Hm, i guess it’s a problem with your connection. I can throttle my speed and everything still works fine here. Got no idea why you’ve got to wait 3 minutes for your website although you’ve got the coolest internet-connection-package from the ads.”

Firefox Throttle Official Site

Thus it’s only available for Windows yet (Apple might have checked the nonsense in throttling speed) here the Mac-Alternative:
mac | Limit bandwidth in Mac OS X using ipfw