Selenium IDE

            The Selenium-IDE (Integrated Development Environment) is the tool you use to develop your Selenium test cases. It’s an easy-to-use Firefox plug-in and is generally the most efficient way to develop test cases.

             It also contains a context menu that allows you to first select a UI element from the browser’s currently displayed page and then select from a list of Selenium commands with parameters pre-defined according to the context of the selected UI element. This is not only a time-saver, but also an excellent way of learning Selenium script syntax.

Merits:

a. Easy to use.

b. Easy to identify element id's and xpath of the id's

De-Merits:
a. It works only with Firefox. So thers is no possibility of browser compatibility testing.
b. IDE script is not customizable.