Element Locator Add-on is very useful to find or locate appropriate web element or control like, text box, button, image, input box, etc. in browser. It will return location string of that particular control. This string is helpful in selenium automation process.
When you right click on particular control or element in Firefox browser, it will populate context menu with very useful XPATH for 'WebDriver' which is very useful in 'findElement' method of selenium 'WebDirver' API.
Here are steps to download and install 'WebDriver' element locator.