Placing mouse over an element may lead to changes in the DOM tree. For example the element may be modified or replaced. It means if you keep a reference to the original element and will try to click on it - it may not work (stale element problem).
This puzzle complicates both recording and playback of a test.
The link below will be replaced and new title assigned to it when you place mouse over it. Click on it to increase the click count.
Click meThe link above clicked 0 times.
The link below will be replaced with identical one when you place mouse over it. Click on it to increase the click count.
Link ButtonThe link above clicked 0 times.