This was made to be simple and straightforward online stopwatch.
No flash or other plugins required. Works on all modern browsers.
Click (or tap) the "Start" button to start the timer.
Click/tap "Stop" to stop counting.
"Split" to get lap time.
"Reset"... It's obvious, isn't it?
If it is still not clear -- just go and tap the buttons. You should get it in maximum 3 clicks...
To add it to your device -- just create a bookmark or, if you are visiting on mobile, click "Add to home screen" button in your browser.