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These days, I had some research on the web performance testing tools and found a very useful and very convenient tool to recommend to you today, it is developed by the google: Page Speed.

What is Page Speed?

Page Speed is an open-source Firefox/Firebug Add-on(you can add it only after you add Firefox 3.0.4  above and Firebug 1.3.3 above). Webmasters and web developers can use Page Speed to evaluate the performance of their web pages and to get suggestions on how to improve them.

How to use Page Speed?

After installed,click the icon at the bottom right corner of Firebug to start it, then you can click the Page Speed tab.Note that, when you want to do a  performance analysis by Page Speed, you must load the page first, then click the “Analyze Performance” button, and  Page Speed will rate each item based on the web performance best practices.Finally, it will array the all items according to importance(as shown above).

Here’s how to interpret the color-code scores:

RED：High priority. These suggestions represent the largest potential performance wins for relatively little development effort. You should address these items first.
YELLOW：Medium priority. These suggestions may represent smaller wins or much more work to implement. You should address these items next.
GREEN： Working fine or low priority. If suggestions are displayed, as indicated with a + sign, they probably represent minor wins. You should only be concerned with these items after you’ve handled the higher-priority ones.
BLUEInformational messages only. Either these items don’t apply to this page or there was a problem in running the test.

ps:the web performance best practices:

1、    Avoid CSS expressions
2、    Combine external CSS
3、    Combine external JavaScript
4、    Defer loading of JavaScript
5、    Enable compression
6、    Leverage browser caching
7、    Leverage proxy caching
8、    Minify JavaScript
9、    Minimize request size
10、    Minimize DNS lookups
11、    Minimize redirects
12、    Optimize images
13、    Optimize the order of styles and scripts
14、    Parallelize downloads across hostnames
15、    Put CSS in the document head
16、    Remove unused CSS
17、    Serve resources from a consistent URL
18、    Serve static content from a cookieless domain
19、    Specify image dimensions
20、    Use efficient CSS selectors
21、    Minify HTML
22、    Minify CSS
23、    Serve scaled images
24、    Avoid bad requests
25、    Specify a character set early

What is the standard?

I’m sorry, there is no official standard.But I am now doing such a thing to share with you:

1, Page Speed Score total score must be 80 or above
2, Serious error not more than three, general error not more than 5
3,The error is not allowed : Avoid CSS expressions, Combine external CSS, Combine external JavaScript, Enable compression, Minify CSS, Minify HTML
4, Allowed error, but must be promptly corrected: Leverage browser caching, Leverage proxy caching, Minify JavaScript, Minimize request size, Optimize images
5, Allowed error, and have time to correct: Minimize DNS lookups, Minimize redirects, Optimize the order of styles and scripts, Parallelize downloads across hostnames, Put CSS in the document head, Remove unused CSS