For the most part, read-ahead accelerators grab all the links on the current page, and then dump them into the cache in the background. When you finally get around to clicking a cached link, the destination page should pop up instantly from your hard drive. How well the process works depends to a large extent on how the software is set up. At their default settings, most browser accelerators prefetch only text, and in some cases they limit the size of the text file. These limitations are necessary so that prefetching doesn't overwhelm your hard drive or your modem, especially when you download lots of graphics files.
Every product uses a different set of defaults, however, and allows a wide variety of tweaks.
Consequently, you'll probably have to tune the accelerator to your style of browsing. We used this function when calling up the latest edition of the Onion, a weekly satirical online newspaper. NetSonic downloaded the initial page and then preloaded all of the main page's 15-odd article links. By the time we were ready to click over, the pages were all cached and appeared instantly. Like NetSonic, it uses both caching and prefetching.