Debugging is the act of identifying and fixing errors in your program. Modern browsers have JavaScript console where errors in scripts are reported. This can be found via right clicking the site and selecting "Inspect Element". You will then see a console screen where errors are printed (if any).
Errors may differ across browsers as each browser has their own JavaScript Engine. There are several tools you can use to debug JavaScript. Microsoft Script Editor is a convenient add-on for Internet Explorer that supports breakpoints and watches for debugging. If you are using other browsers, debugging it locally own your computer or searching for an add-on or a online text editor is how you would approach debugging. Firefox has Firebug, which we will talk about in the next section.