If you are a web designer or developers and imagine that you have to grab some color from a web page but your designing tool i.e. Photoshop is not working then what you will do to get rid of this situation, how you will grab the colors. The solution to such problems or situations is “Rainbow Color Tools”.
“Rainbow color tools” is a Firefox extension that enables you to grab colors from web pages quickly and easily with a single click.

Once installed, click on “Rainbow Color Tools” icon in the bottom right corner of the browser. A small colorbox will be displayed containing the color of web page area, you hover over the cursor. Now to grab color, click on that area, the color code will be displayed in the colorbox from where you can copy or bookmark the color.



As I am a web developer , I found it very helpful while working on my projects.
Get “Rainbow Color Tool” from there
Firefox: Download Here


JSON is a popular way to format AJAX responses, as it’s more compact than XML and essentially a JavaScript object, but it can be a real pain to work with due to uncooperative browsers. It’s easy enough to view XML in a web browser, which is good for testing, but JSON responses cause a download prompt to open. This makes it harder to verify that an AJAX request is working properly.

Normally when encountering a JSON document content type "application/json", Firefox simply prompts you to download the file. With the JSONView extension, JSON documents are shown in the browser similar to how XML documents are shown. The document is formatted, highlighted, and arrays and objects can be collapsed. Even if the JSON document contains errors, JSONView will still show the raw text.

 
Once you've got JSONView installed, check out the link below to see ho how JSON data looks like.


JSONview is firefox extension and can be downloaded from there

Firefox: Download Here


  

LastPass is a free online password manager and Form Filler that makes your web browsing easier and more secure. LastPass supports all major internet browsers i.e. Chrome, Firefox, Internet Explorer, and Safari as a browser extension (and Opera, Opera Mini and more via Bookmarklets ).
To import Chrome passwords (Windows only currently), you'll also need full Windows installer available on http://lastpass.com/


You can import from most major password storage vendors such as RoboForm,  1Password, KeePass, Password Safe, MyPasswordSafe, Sxipper, TurboPasswords, Passpack, Firefox and Internet Explorer's built-in password manager and export too.
LastPass captures passwords that other managers won't including many AJAX forms, and allows you to make strong passwords easily.  If you're having issues saving a site please watch our screencast on complex logins

http://lastpass.com/video.php?&feature=saveall#media .


Your sensitive data is encrypted locally before upload so even LastPass cannot get access to it.  LastPass also offers a premium upgrade which includes native mobile apps (iPhone, BlackBerry, Windows Mobile, Android, WebOS (Palm), Symbian S60), additional multi-factor options and priority support.
Users, who use Internet explorer,they should download a standalone exe file from their homepage.
Lastpass is available nearly for all browsers. You can get it from there.

Firefox: Download Here
Chrome: Download Here
Opera:  Download Here
Internet Explorer: Download Here


FastestTube is an extension for Opera, Safari, Mozilla Firefox and Chrome. The extension adds a simple drop-down below the YouTube videos enabling you to select and download the video in any format you want to that too without much fuss. It’s the best YouTube downloader tool ever.

 
Get Opera Fastest Tube from there