When i started using Selenium i found it difficult to perform actions (hover,click..etc) on hidden elements, which becomes visible only when hovered on some other element. so i hope this will help others, you can use any of the following ways..
For example, to upvote a comment in this page,i need to hover on the context (i.e. comment) to make upward arrow visible, then i need to click on it. But using javascriptExcecuter you can execute this in one step.
//this can be used even if the element is not visible
//if you want to hover over the element, replace click() with hover()
((JavascriptExecutor)driver).executeScript("$('element_selector').click();");
OR
you can use Actions class rather than using the Keyboard or Mouse directly.
It implements the builder pattern: Builds a CompositeAction containing all actions specified by method calls
Keyboard, Mouse and TouchScreen have all been deprecated and removed from WebDriver with the last patch: code.google.com/p/selenium/source/browse/java/CHANGELOG
