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The Exceptional Performance team has identified a number of best practices for making web pages fast. The list includes 35 best practices divided into 7 categories.
For details – >http://developer.yahoo.com/performance/rules.html
For test your website speed, There are some site such as->
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Prefer asynchronous resources
Combine images using CSS sprites
Combining images into as few files as possible using CSS sprites reduces the number of round-trips and delays in downloading other resources, reduces request overhead, and can reduce the total number of bytes downloaded by a web page.
Serve resources from a consistent URL
Sometimes it's necessary to reference the same resource from multiple places in a page — images are a typical example. Even more likely is that you share the same resources across multiple pages in a site such as .css and .js files. If your pages do need to include the same resource, the resource should always be served from a consistent URL. Ensuring that one resource is always assigned a single URL has a number of benefits. It reduces the overall payload size, as the browser does not need to download additional copies of the same bytes. Also, most browsers will not issue more than one HTTP request for a single URL in one session, whether or not the resource is cacheable, so you also save additional round-trip times. It's especially important to ensure that the same resource is not served from a different hostname, to avoid the performance penalty of additional DNS lookups.
Optimize the order of styles and scripts
Correctly ordering external stylesheets and external and inline scripts enables better parallelization of downloads and speeds up browser rendering time
Properly formatting and compressing images can save many bytes of data.
Specifying a character set early for your HTML documents allows the browser to begin executing scripts immediately.
In order to load a page, the browser must parse the contents of all <script> tags, which adds additional time to the page load. By minimizing the amount of JavaScript needed to render the page, and deferring parsing of unneeded JavaScript until it needs to be executed, you can reduce the initial load time of your page.
<script>
Use an Expires header to control how your site is cached on visitors' browsers.
Running multiple servers with default ETag settings can prevent 304 responses.
Compressing resources with gzip or deflate can reduce the number of bytes sent over the network.
gzip
deflate
<IfModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file \.(html?|txt|css|js|php|pl)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</IfModule>
or
# BEGIN Compress text files
<ifModule mod_deflate.c>
AddOutputFilterByType DEFLATE text/html text/plain text/xml application/xml application/xhtml+xml text/css text/javascript application/javascript application/x-javascript
</ifModule>
# END Compress text files
Minify HTML
Compacting HTML code, including any inline JavaScript and CSS contained in it, can save many bytes of data and speed up downloading, parsing, and execution time.
Compacting CSS code can save many bytes of data and speed up downloading, parsing, and execution time.
Compacting JavaScript code can save many bytes of data and speed up downloading, parsing, and execution time.
Moving inline style blocks and <link> elements from the document body to the document head improves rendering performance.
<link>
Avoid a character set in the meta tag
Specifying a character set in a meta tag disables the lookahead downloader in IE8. To improve resource download parallelization, move the character set to the HTTP Content-Type response header.
Read more
Minify CSS
Leverage browser caching
Setting an expiry date or a maximum age in the HTTP headers for static resources instructs the browser to load previously downloaded resources from local disk rather than over the network.
Solution:
"The following cacheable resources have a short freshness lifetime. Specify an expiration at least one week in the future for the following resources:..."
I search google and found an easy way to solve this issue.
Put this code into your .htaccess file and upload it:
<FilesMatch "\.(ico|jpg|jpeg|png|gif|js|css|swf)$">
<IfModule mod_expires.c>
ExpiresActive on
ExpiresDefault "access plus 30 days"
Header unset ETag
FileETag None
</FilesMatch>
Now, wait few mins, and recheck your Google Page Speed Score. You will see your Page Speed Score will be improved. My Google Page Speed Score improved and jumped to 98/100.