Scratchpad is a tool which is include in Mozilla Firefox browser. It is is essentially a live JavaScript editor and prototyping tool. You can access it through menu Tools -> Web Developer Scratchpad. Or you can just simply open it using shortcut Shift+fn+F4 (In Mac OS X).

Unlike other tools such as Web Console or Firebug, Scratchpad lets you edit larger chunks of JavaScript code, then execute it in various ways depending on how you want to use the output. It wont interpreting single line of code at a time. Using the Scratchpad, a developer can access the current page’s objects, variables and script. In addition, complete functions can be written and tested in the editor within the scope of the live page. These changes can then be attached and saved with the current application.

Although this tools is very handly and friendly for developer, for some people it can be annoying and irritating. There are complaints about it. Eg, sometimes, when you start to type in an email or a form, Javascript Scratchpad opens, and you’re typing in that window. Or Scratchpad is just opened whenever you open a browser tab and accessing a website.

So how to deal with that?

1. Start Firefox in Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes). To do the Safe mode, follow these steps:

2. Various Web Developer tools each have their own pref on the about:config page to enable or disable them.

•     devtools.scratchpad.enabled
•     devtools.inspector.enabled

Follow these steps:

Set those configs to false on the about:config page to disable the Scratchpad. All you need to do is just double click on those settings to toggle it true/false.

That should work. If it doesn’t, then you can try to reset your Firefox settings back to its factory default :)

Ref:

• Troubleshoot Firefox issues using Safe Mode
  Reset Firefox – easily fix most problems