Some browsers have built-in utilities that can help you diagnose syntax errors. There will come a time when you have written a program and you can't figure out why it won't work by merely examining the code. These utilities can save you lots of time. Not all browsers have one, but here are the debuggers we have found. Even if your favorite browser is not listed below, it is advisable keep one of these around, even if you only use it to check JavaScript syntax.

PC
Explorer version 5. After executing broken JavaScript code, this browser displays a small exclamation point icon in the lower left corner of the window in the status bar. Clicking that icon will report syntax errors.

Netscape 4.7. After executing broken JavaScript code, you simply type javascript: (that's lower case javascript followed by a colon) into the address field of the browser and hit return. You get a JavaScript error window.

Mac
Netscape 4.7. After executing broken JavaScript code, you simply type javascript: (that's lower case javascript followed by a colon) into the address field of the browser and hit return. You get a JavaScript error window.

Netscape 6. After executing broken JavaScript code, go to the Tasks menu, select Tools, and then JavaScript Console.

Note: While good for catching syntax errors, these will be of little use catching logic errors.