How to find causes of interferences?

Question

My dropdown button doesn't work. I tried it on JSFiddle and it work perfectly.

I'm using Chrome browser.

There is a tool or method to help me to find the problem?

Epilogue:

Using "Visual Event" I tracked the point of bootstrap.js where the click event is handled. Unfortunately, the problem wasn't there, but in a piece of code that was executed later, that closed instantly the dropdown list. So it appear like a bootstrap problem with buttons.

I have found that the interference, in my case, is due to an extension of Chrome: ToutApp Extension for Gmail.

Disabling ToutApp the dropdown buttons have begun to work correctly!

Answer 1

Chrome developper tools (F12)

There is also this extension that I like to use, it helps to see what code is called for every events bound to DOM elements: Visual Event

Answer 2

You can use Google chrome -> right click then -> inspect element

Answer 3

you can inspect your element as said before and check the tags. mostly if the the tags are not closed properly this may cause problems.

you can use firebug extension on Firefox or inspect element in Chrome (that should be enough to solve to problem).