Here is a Java applet to let you play with the sieve of Eratosthenes. It may take a few seconds to start up or reset.
To eliminate all multiples of 2 (except 2 itself), press 2. Likewise, to eliminate all multiples of a number (except itself), press its button. Do not hesitate to experiment.
Anytime, you can start over by pressing the Reset button to start over. You can select a new size for the table by setting the Size field, and then press Reset.
If you are interested, you can look at the source code.