Values in memory will be lost if page is reloaded.
In bases other than base 10 (decimal), fractional values will be rounded down.
If you click on a button and then later press the enter key for "=", the act of pressing enter might also cause the last key you have clicked on to be pressed again.
Check the "Hovering tooltips" box if you are unsure what some calculator functions do, then hover your mouse over the button in question.