The easiest and simplest YouTube downloader is this extension. It adds a button below the video to download in different formats that are available for that video i.e. FLV, 3GP, MP3, MP4 and 720p HD and 1080p Full-HD qualities. 

New Features :
  •  Video-title as file-name.
  •  HD download link visible only when high-definition version is available.
  •  Supports all new 1080p FULL-HD video downloading
  •  Latest v 3.X works with new YouTube layout
Easy YouTube Downloader is a firefox extension and can be downloaded below.

Firefox: Download Here

Auto fill, a small but very powerful extension that let you fill forms automatically when pages load. It proves to be an itch in the nose when we have fill form now and often while surfing the web. It is for those people who want straightforward form filler without any bells and whistles.


After installation, click the “options button” to configure the auto filler. There you can specify the form controls and the required data. You can also add or remove controls according to your requirements. The “Formfiller” will automatically fill the fields if that web page contains the defined fields.

Now take a look at its features it offers

Features:
  • Ultimate form control – autofill text input boxes, textarea, password fields, hidden fields, and even iframe-based WYSIWYG edit boxes; drop-down menus and listboxes; checkboxes and radio buttons.
  • Regular Expressions – it also support Regex, so define powerful expressions to 
  • identify the fields.
  • Site filtering – restrict autofill on a per-site basis
  • Exceptions – if you want to restrict autofiller for some sites, then in specify the 
  • websites to exclude from autofill.
  • Import/Export – transfer your settings to another computer or to the Autofill 
  • extension for Google Chrome

Auto filler is available for Mozilla Firefox and Google Chrome both. You can download it from there.
Chrome: Download Here
Firefox: Download Here

Visual firebug is a chrome extension alternative to firebug. It lets you edit online pages easily and quickly with the help of its visual GUI. It helps visual designers and developers build their sites in a much better way. They can user different controls to edit the page, easily create and modify the style sheets.

When you will make changes to the web page, its CSS will be displayed at the top of the control as you can see in the figure.  

Web designers can use its visual GUI so that they don’t need to open Photoshop, azure or other design tools. Visual firebug is available for Google Chrome and can be downloaded from there.
Chrome: Download here

If you are a web developer or web designer then this extension is only designed for you to make your development simple, easy. You must install firebug which is a Firefox extension. Firebug offers you a wide range of functionalities to
  • Inspect HTML and modify style and layout in real-time
  • Use the most advanced JavaScript debugger available for any browser
  • Accurately analyze network usage and performance
  • Extend Firebug and add features to make Firebug even more powerful
  • Get the information you need to get it done with Firebug.
Other features that this extension offers are
  • Monitor and analyze network performance, to understand what elements might be slowing your website down.
  • Inspect the HTML code by viewing the source of any page in real time, filtering specific elements and editing them if necessary.
  • Inspect and edit CSS and JavaScript as well.
  •  Test your pages to see if they contain errors, and debug them with the help of Firebug.
  • Use the Firebug rulers and boxes to analyze and optimize the layout on your pages.
Firebug Lite for Google Chrome is now available. you can download it from the here

Chrome: Download here