1.
Web Performance Optimization (WPO)
General, Server Side and Technology level Techniques

2.
Outline
General Level Optimization
1
2
Importance of Web Performance
Server Side Optimization3
Technology Level Optimization4
Performance Measurement Sites5
References6

3.
Importance of Web Performance
 Even a few seconds delay is enough to create an unpleasant user experience.
 57% of online shoppers will wait 3 seconds or less before abandoning the site.
 Google engineers found that users begin to get frustrated with a site after waiting just
400 milliseconds – literally the blink of an eye – for web pages to load.
Source – Aberdeen Group

4.
Levels of Optimization
General
Level
• Content
• Cookie
• CSS
• JavaScript
• Image
• Mobile
Server
Level
Technology
Level

5.
Levels of Optimization

6.
General Level Optimization
1. Minimize HTTP Requests
 Most of the time is tied up in downloading all the components in the page:
images, stylesheets, scripts, Flash, etc.
 How to minimize HTTP Request?
 Combined files are a way to reduce the number of HTTP requests by
combining all scripts and CSS into a single stylesheet and CSS respectively.
 CSS Sprites are the preferred method for reducing the number of image
requests.
 Image maps combines multiple images to single image.
 Browser Cache Usage - 40-60% of daily visitors to your site come in with an
empty cache.

7.
2. Put Stylesheets at the Top
 Various research shows that moving stylesheets to the document HEAD makes pages
appear to be loading faster.
 The problem with putting stylesheets at the bottom of the document is that it
prohibits progressive rendering and user’s stuck viewing a blank white page.
 Placing stylesheets in the HEAD allows the page to render progressively.
 Vital for pages with a lot of content and for users on slower Internet connections.
General Level Optimization

8.
3. Minify JavaScript and CSS
 Minification reduces response time and the size.
 Few popular tools for minifying are:
 JSMin
 YUI Compressor
 Google Closure Compiler
 Obfuscation is an alternative optimization.
 Both methods achieves fairly the same size reduction (Minification achieved a 21%
size reduction, where 25% for obfuscation), but obfuscation is bit risky with JavaScript.
 Should minified in-line JS and CSS as well (5% reduction).
General Level Optimization

9.
4. Avoid CSS Expressions
 CSS expressions are a powerful (and dangerous) way to set CSS properties
dynamically.
 Supported in IE starting with version 5, but were deprecated starting with IE8.
 Adding a counter to the CSS expression allows us to keep track of when and how
often a CSS expression is evaluated.
 Solutions
 Use one time expression instead of CSS expression.
 For Dynamic throughout style property, use Event handler.
background-color: expression( (new Date()).getHours()%2 ? "#B8D4FF" : "#F08A00" );
General Level Optimization

10.
5. Make JavaScript and CSS External
 Using external files produces faster pages.
 JS and CSS files are cached.
 In-lined increases the document’s size.
 Many documents could re-use them.
 To reduce HTTP requests in the front page:
 In-line JavaScript and CSS, but dynamically download the external files after
finished loading.
General Level Optimization

11.
6. Choose <link> over @import
 The difference between them is that @import is the CSS mechanism to include a
style sheet and <link> the HTML mechanism. However, browsers handle them
differently, giving <link> a clear advantage in terms of performance.
 In IE @import behaves the same as using <link> at the bottom of the page, so it's
best not to use it.
General Level Optimization

12.
7. Put Scripts at Bottom
 Browser do not download more than two components in parallel per hostname.
 Block parallel downloads across all hostnames.
 Block rendering of everything below them in the page.
 Never uses document.write.
General Level Optimization

13.
8. Remove Duplicate Scripts
 Two of Ten top sites contains duplicated script.
 Main factors increase the odds of a script being duplicated in a single web page is
team size and number of scripts.
 Hurt performance by creating unnecessary HTTP requests and wasted JavaScript
execution.
 Solutions
 Implement a script management module in your template system.
 The typical way to include a script is to use the SCRIPT tag in your HTML page.
 An alternative in PHP would be to create a function called InsertScript.
<script type="text/javascript" src="menu_1.0.17.js"></script>
<?php insertScript("menu.js") ?>
General Level Optimization

14.
9. Optimize Image
 Image needs to be optimized before you FTP those images to your web server, after
designer is done with creating the images for your web page.
 Key things are
 Check the GIFs, whether palette size corresponding to the number of colors in
the image.
 Try converting GIFs to PNGs (except for animations).
 Run pngcrush (or any other PNG optimizer tool) on all your PNGs.
 Run jpegtran on all your JPEGs.
General Level Optimization

15.
10. Optimize CSS Sprites
 Arranging the images horizontally (makes the smaller file size).
 Combining similar colors in a sprite helps you keep the color count low, ideally under
256 colors so to fit in a PNG8.
 Don’t leave big gaps between the images in a sprite.
 It makes the user agent requires less memory.
General Level Optimization
11. Keep Components Under 25kb for Mobile Site
 iPhone wont cache components > 25K (uncompressed size).
 Minification is important because gzip alone may not be sufficient.

16.
12. Don’t Scale Images in HTML
 Do not use a bigger image than you need.
 If you need
<img width="100" height="100" src="mycat.jpg" alt="My Cat" />
then mycat.jpg should be 100x100px, rather than scale down from 500x500px image
General Level Optimization

17.
13. Make favicon.ico Small and Cacheable
 Browser will always request it, better not to respond 404.
• Cookies are sent every time its requested.
• Also interferes with the download sequence in IE.
 Solutions
 Make it small, preferably under 1K.
 Set Expires header when you feel comfortable.
 Imagemagick can help you create small favicons.
General Level Optimization

18.
14. Avoid Empty Image src
 Image with empty string src attribute occurs more than one will expect.
 It appears in two form: –
 Straight HTML  <img src=" ">
 JavaScript  var img = new Image();
img.src = "";
 Browser makes another request to your server.
 Cripple your servers by sending a large amount of unexpected traffic.
 Waste server computing cycles.
 Possibly corrupt user data.
 HTML5 instruct browsers not to make an additional request.
 Empty image src can destroy your site.
General Level Optimization

19.
15. Avoid Redirects
 Redirects are accomplished using the 301 and 302 status codes.
 Redirects slow down the user experience.
 Nothing can be rendered
 Round-trip request
 Add Expires headers to cache redirects.
 Wasteful Redirect, i.e. when a trailing slash (/) is missing from a URL that should
otherwise have one.
 This is fixed in Apache by using Alias or mod_rewrite, or the DirectorySlash directive
if you're using Apache handlers.
HTTP/1.1 301 Moved Permanently
Location: http://example.com/newuri
Content-Type: text/html
General Level Optimization

20.
16. Make Ajax Cacheable
 Expires or Cache-Control header.
 Adding a timestamp to the URL – &t=1190241612.
 When it has been modified, send with a new timestamp.
 The most important way to improve the performance of Ajax is to make the
responses cacheable
17. Avoid 404’s
 Ineffectual response (i.e. 404 Not Found) is totally unnecessary and will slow down
the user experience without any benefit.
General Level Optimization

21.
18. Reduce Cookie Size
 HTTP cookies are used for a variety of reasons such as authentication and
personalization.
 It's important to keep the size of cookies as low as possible to minimize the impact
on the user's response time.
 Eliminate unnecessary cookies.
 Keep cookie sizes small.
 Setting cookies at the appropriate domain level.
 Set an Expires date appropriately. An earlier Expires date or none removes the cookie
sooner, improving the user response time
General Level Optimization

22.
Levels of Optimization

23.
1. Implement Content Delivery Network (CDN)
 The users proximity has an impact on response times.
 Solutions
 Use a CDN: Akamai Technologies, EdgeCast, Amazon CloudFront, or level3.
 Distribute your static content before distributing your dynamic content.
 At Yahoo, using a CDN improved response times >= 20%.
Server Level Optimization

24.
2. Reduce DNS Lookups
 Domain Name System (DNS) maps hostnames to IP addresses.
 On average, takes 20-120 Milliseconds.
 IE caches :
DnsCacheTimeout : 30 minutes
 Firefox :
network.dnsCacheExpiration : 1 minute
(Fasterfox changes this to 1 hour)
 Reducing hostnames reduces the DNS lookups, But it reduces parallel downloads.
 Better to split these components across at least two but no more than four
hostnames.
Server Level Optimization

25.
3. Split Components Across Domains
 Splitting components allows you to maximize parallel downloads.
 Make sure you're using not more than 2-4 domains because of the DNS lookup
penalty.
 For Instance, you can host your HTML and dynamic content on www.example.org
and split static components between static1.example.org and static2.example.org.
Server Level Optimization

26.
4. Use Cookie-free Domains for Components
 Create www site and sub-domain.
 that sub-domain is cookie-free.
 Buy a whole new domain if already set on domain without www.
 Yahoo! uses yimg.com,
 YouTube uses ytimg.com,
 Amazon uses images-amazon.com and so on.
 Some proxies might refuse to cache the components that are requested with
cookies.
Server Level Optimization

27.
5. Add Expires or Cache-Control Header
 Use "Never expire" policy for static components by setting far future Expires
header.
 For dynamic components, use an appropriate Cache-Control header to help the
browser with conditional requests.
 Avoid unnecessary HTTP requests on subsequent page view after the first visit.
Server Level Optimization

28.
6. Gzip Components
 Gzip is effective compression method compared to deflate.
 Key Features are
 Reduces response times.
 The response size ~ 70% reduction.
 90%+ of browsers support gzip.
 Compress any text responses.
 Image and PDF files SHOULD NOT be gzipped.
 In Apache, the module configuring gzip depends on your version: Apache 1.3 uses
mod_gzip while Apache 2.x uses mod_deflate.
Server Level Optimization

29.
Levels of Optimization

30.
General Guidelines
 Keep the Joomla! Version updated.
 Choose extensions wisely.
 Deactivate unused extensions, upgrade used.
 Simplify your templates as much as possible.
 Use Cache.
 Optimize the MYSQL Statements.
 Use limited number of Records in SQL.
Enhance Joomla! Web

31.
1. Flush Buffer Early
 Normally, it may take 200 to 500ms for the backend server to stitch together the
HTML page, once a user request a page.
 The browser remains idle until data is received.
 In PHP flush() function allows you to send your partially ready HTML response to
the browser so that the browser can start fetching components while your backend
is busy with the rest of the HTML page.
 The benefit is mainly seen on busy backend or light frontend.
 Flushing after the HEAD is optimal, as it allows to include any JS and CSS.
 Example
Technology Level Optimization
... <!-- css, js -->
</head>
<?php flush(); ?>
<body>
... <!-- content -->

32.
Performance Measurement Sites
 http://www.webpagetest.org/
 http://tools.pingdom.com/
 http://gtmetrix.com/
 http://www.websiteoptimization.com/services/analyze/
 http://site-perf.com/
 https://developers.google.com/speed/pagespeed/insights
 http://loadimpact.com/page-analyzer
 http://newrelic.com/