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You can find out those error on console. Console shows us helpful information about the error, like which line of the web page the error occurred and description of the error but the question is from where we will find the console? Well every browser have there own way to track console.
There are some popular web browsers console
The Chrome JavaScript Console:
To open the JavaScript console, click the Customize menu button and choose More tools→Developer tools Select Console tab. Or use the keyboard shortcut Ctrl+Shift+J (Windows) or command-Option-J (Mac).
The Firefox Console:
To open the console, on Windows click the tab in the top left of the browser and select Web Developer→Web Console and On a Mac, select Tools→Web Developer→Web Console. Or use the keyboard shortcuts Ctrl+Shift+K (Windows) or command-Option-K (Mac)
The Safari Error Console:
To open Safari’s error console choose Develop→Show Error Console (or, if you’re on a Mac, use the Option-c-C keyboard shortcut) bt in Mac Develop menu isn’t normally turned on when Safari is installed. To turn on the Develop menu Choose Safari→Preferences. click the Advanced button. Turn on the “Show Develop menu in menu bar” box then close the Preferences window.
When you restart Safari, the Develop menu will appear between the Bookmarks and Window menus in the menu bar at the top of the screen. Select Develop→Show Error Console to open the console.
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