The purpose of this activity is to experience what it's like to use a web page with screen reader software.
Go to WebAnywhere, a free, public screen reader implemented as a web proxy. Look over the instructions (particularly the keyboard shortcuts!) and play with it a bit on WebAnywhere's home page.
Then use WebAnywhere to visit this page (note that you won't see anything, but you'll hear it), and try to answer these questions:
Assuming you figured out the answer to #1, now go to the real web page and see how easy it is to answer these questions visually by comparison.
WebAIM (an organization at Utah State University) has created several good simulations of accessibility problems.
Mac OS X has a built-in screen reader called VoiceOver (which you can turn on using System Preferences / Universal Access). For Windows, the screen readers JAWS and Window Eyes both have time-limited trial versions that you can install to see what screen reading is like.
ADesigner helps you check the degree of accessibility of a web page to a screen reader. Among its nice features is a visual display (for the sake of sighted designers) of the time cost of reaching each HTML node in the page using a typical screen reader.