Website optimization

Web Site Optimization

Why ??? To know some basic rules/practices while

developing a web-application. Whom ???

Web devlopers who are working html,css,js and other web technology.

What ??? Its difficult to implement all the points that we

discuss today. But we can check something.


In this session we'll go through 4 basic stuffs. Basic optimization rules Optimizing assets (images, scripts, and styles) Optimizations specific to scripts Optimizations specific to styles


Decrease Download Sizes Keep all the assets as lightweight as possible Creating lean HTML code

Make Fewer HTTP Requests Combine scripts and style sheets Use image sprites Avoid redirects Avoid frames

Basic Optimization Rules


Use a Content Delivery Network (CDN) Host Assets on Different Domains but Reduce

DNS Lookups Place Assets on a Cookie-free Domain Split the Assets Among Domains Use the Header Expiry/caching Serve gzipped Content Handling web images

Optimizing Assets


Using a Content Delivery Network – CDN CDN is a network of servers in different

geographical locations. Each server has a copy of a site’s files. When a

visitor to your site requests a file, the file is delivered from the nearest server

Its expensive :(

Optimizing Assets


Why host assets on different domains ?????Seems its an extra headache for me !!!!! :( The biggest impact on end-user response times

is the number of components in the page. Each component requires an extra HTTP

request. Browser allows a limited number of component

for parallel downloading per host. (mostly only 2)

Optimizing Assets


Lets see what if there is parallel download....Lets assume we have 10 components along with

the page.

Optimizing Assets


What if components are on different domains.. ( Create subdomains and host assets )

Optimizing Assets


Warning !!!!!!!!!! Depending on your bandwidth and CPU speed,

too many parallel downloads can degrade performance.

It takes about 20-120 milliseconds for DNS (Domain Name System) to resolve IP address for a given hostname or domain name and the browser cannot do anything until the process is properly completed.

Optimizing Assets


Place Assets on a Cookie-free Domain If you set a lot of cookies, the request headers

for your pages will increase in size, since those cookies are sent with each request.

If you use subdomains to host your assets, you need to make sure that the cookies you set are for your canonical domain name (e.g. www.example.org) and not for the top-level domain name (e.g. example.org).

Optimizing Assets


Customized Expiry header..... By using a customized Expiry header, your web

components like images, static files, CSS, Javascript skipped unnecessary HTTP request when the same user reload the page for the second time.

Setting the Expires header in Apache is easy: Lets see the example on next slide

Optimizing Assets


Example Expiry header.....Add an .htaccess file that contains the following

directives to the root folder of your i1 and i2 subdomains

ExpiresActive On

ExpiresDefault "modification plus 10 years"

If you want, you can even set an expiration date per file type:

ExpiresActive On

ExpiresByType application/x-javascript "modification plus 2 years"

ExpiresByType text/css "modification plus 5 years"

For more : http://httpd.apache.org/docs/2.0/mod/mod_expires.html

Optimizing Assets


Handling Web Images... Images are important part of your website.

However if they are not properly optimize, they can become a burden and end up utilizing unpredictably large amount of bandwidths on daily basis.

Don’t Scale Images. Always practice inserting the width and height for each images. Also don’t scale down an image just because you need a smaller version on the web. For example: Do not force scale a 200×200 px image to 50×50 px for your website by altering the width and height. Get a 50×50 px instead.

Optimizing Assets


Serve gzipped Content... Apache 1.x and 2.x can automatically compress

files, but neither one comes with a compressor enabled by default. Enabling compression reduces CSS, HTML, and JavaScript file sizes by 55-65% and speeds up overall page load times by 35-40%.

Apache uses plug-in modules to add functionality. For Apache 1.x, use the free mod_gzip module to compress files. For Apache 2.x, use mod_gzip or the built-in mod_deflate module.

Optimizing Assets


For gzipped Content... The mod_gzip module can be used with Apache 1.x or 2.x,

but it doesn’t come with either Apache distribution. You’ll need to download and install it separately.

Add the following lines to your server configuration file or to a site’s “.htaccess” file:

<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>

Optimizing Assets


For gzipped Content... For IIShttp://www.smallworkarounds.net/2009/01/aspnet-iis-tricks-using-

gzip.html

http://jeeshenlee.com/2010/08/01/how-to-gzip-on-asp-net-and-godaddy/

Optimizing Assets


Merge .js f iles Minify scripts

For Minify http://compressor.ebiene.de/ http://javascriptcompressor.com/

Place scripts at the bottom of the page Remove duplicates

Javascript Optimizations


Merge script files …. You should aim for your JavaScripts to make as

few requests as possible; ideally, this also means that you should have only one .js file. This task is as simple as taking all .js script files and placing them into a single file.

Example : http://code.google.com/p/phpflair/

Javascript Optimizations


Merge and Minify For Minify http://compressor.ebiene.de/ http://www.cleancss.com/

Place styles at the top of the page Ban Expressions

#content { left: expression(document.body.offsetWidth) }

CSS Optimizations


#element-id{

background-image: url(image.png);

background-position: -8px -8px;

width: 16px;

height: 16px;

}


Firebug’s Net panel for Firefox, at http://www.getfirebug.com

YSlow, Yahoo!’s performance extension to Firebug, at http://developer.yahoo.com/yslow/

LiveHTTP Headers for Firefox, at http://livehttpheaders.mozdev.org/

Fiddler — for IE, but also a general-purpose packet sniffer, at http://www.fiddlertool.com/fiddler/

Web Inspector for Safari, at http://webkit.org/blog/?p=41

TOOLS FOR PERFORMANCE OPTIMIZATION

Technology

Website optimization