How do you trace the sites visited on the internet?

to find websites that a computer has visited, you are referring to the "history". It is fairly easy to find a computers history (given that a user did not wipe the history clean).

For example in internet Explorer 7 click the little star on the top left, 3 tab over you will see a history section, click it. This will display a drop down list of site vistited and will be sorted by time.

Each internet browser software has a differnet way to check the history, what browser are you using?

Fire fox