They are millions of websites available, some are true tools for us web designers and developers. I have compiled 15 excellence sites for web designers and developers, that should definitely be added to your bookmarks.

1. Script Src

Tired of hunting down the script tag for the latest version of your Javascript Library of choice? Yeah so is everyone else this is the most current library of script tags with just a mouse click away.

2. When Can I Use..

When Can I Use is a compatibility table that shows which upcoming web technologies are compatible with each existing browsers. You can select from HTML5, CSS3, SVG and a multitude of other technologies, then specify which browsers and versions you want to know about, and it spits out a table that tells you what’s supported and what’s not (including partial support).

3. Test Everything 100+ Tools

This site is a definitive must have for your bookmarks it’s should be place close to the top of your bookmarks, as the name says, Test Everything allows you to test lot of things such as XHTML and CSS validation, testing sites in different browsers, Page Rank, back-links, sharing logins to various websites and a lot more.

4. Browser Sandbox

Cross browser compatibility is definitely one of the biggest problems a web developer has to face in his/her daily job. The browser sandbox lets you run any Windows browser from the web. The only bad thing is that you must run a Windows machine: The app does not work on Macs and GNU/Linux unless you run a virtual Windows OS.

5. Ems Chart

Using a relative unit such as EM is a great way to maintain the vertical rhythm of a web page when a user re-sizes text in their browser. Constantly reaching for a calculator to compute the correct EM value to use every time you need to is also a great way to drive yourself mad.

6. Pingdom Tools

This is another excellence tool,  It’s performs a full loads of a complete HTML page including all objects (images, CSS, JavaScript, RSS, Flash and frames/iframes). It mimics the way a page is loaded in a web browser.

7. Browize

Browize is a web-based solution that will be of aid to developers that need to test any application they are laboring at in different screen configurations, and who want to avoid the hassle of changing it manually each and every single time.

8. MySQL Format Date

MySQL Format Date helps you format your dates using the MySQL DATE_FORMAT function.  Just select a common date format and then change it to your suit your needs. The MySQL DATE_FORMAT code will be generated at the bottom of the page which you can then copy into your query.

9. Smush it!

“A picture is worth a thousand words” but they’re also well-known to use a lot of bandwidth. Images can be optimised for the web using programs like Photoshop; but if you don’t own a copy of this software or simply don’t have any idea on how to do it. This tool is awesome for you, brought to you by the Yahoo developers network. Smush.it is an online tool that will reduce your image size without reducing their quality.

Are you a WordPress users, a very handy plugin for your favorite blogging engine is available here.

10. Em Calculator

Em Calculator is a small JavaScript tool which helps making scalable and accessible CSS design. It converts size in pixels to relative em units, which are based on a text size.

11. .htaccess editor

A .htaccess file is a must have for any website. If you know have to write one congratulations to you but if you don’t know how to write one? No problem, just visit this site to create your .htaccess file using a wizard. Note: This site doesn’t allow very advanced settings, but the results are great for 95% of the websites you’ll make.

12. CSS Compressor

Today, CSS files can become huge and use a lot of server bandwidth. This tool named CSS Compressor can reduce the size of any CSS file by removing comments, indentation, compress colours (colors) and more.

13. Javascript Compressor

Like CSS, JavaScript files can become huge and consume a lot of server bandwidth. So this tool happily called Javascript Compressor can reduce your written JavaScript code to make sites load a bit faster.

14. Color Scheme Designer

A good colour (color) choices should never be taken for granted in web design. A bad colour (color) choice or combination can have the same negative effective as poorly laid-out content or can create the same frustration as an excessively slow loading page. This is where this tool is excellence to use this is a must for anyone .

15. W3C Markup Validation Service

The W3C validation service checks the markup validity of web documents in HTML, XHTML, RSS/Atom feeds, CSS style sheets and finds broken links.

If you don’t want to have 15 different bookmarks in your favourites/bookmarks just book mark this post for future reference.