There are a lot of stopwatches out there, they all fundamentally do the same thing but there are subtle and important differences.
For example some stopwatches only run on certain devices, this is the case with most apps. A stopwatch app that was created for the iPhone for example will not work on an Android phone.
But just because it's a website doesn't mean it will work on any device. For example if a website uses Flash it will not work on the iPhone or iPad. Websites that use Java might have similiar problems.
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