This page demonstrates a memory leak in IE8. There is no leak in IE6, IE7, Firefox, Chrome, ....
For more information and context, see my blog.
To begin, bring up the Windows Task Manager. Make sure it's displaying memory usage, and find the appropriate iexplore.exe in the list. Note the starting memory size. Click start below. In IE8 (with defaults below), you should see memory grow by about 1 MB every 5 seconds or so, or about 13 MB per minute, which is 1 GB in 78 minutes. You can see more or less growth by adjusting the HTML and replications below.
The following elements leak: form, button, input, select, textarea, a, img, object. For example, this means if you change the HTML to replicate to <span></span>, you will see no leak.
View source for more details.