Does your website have a habit of loading slowly? Sure you could blame it on your web server, but there is actually quite a lot you can do yourself to improve the loading time and performance of your website. YSlow is a Firefox add-on that integrates with Firebug to analyze a website and suggest ways of improving the performance of that site.
When you run YSlow on a web page it will analyze the page based on a set of rules (outlined below) then grade the web page based on these rules. Yslow also analyzes each component of the page and returns statistics as well as suggestions on how to improve each component of your site to achieve faster performance. As an example I ran YSlow on the Smashing Magazine website and discovered that they could improve their performance by simply combining background images into a CSS Sprite as well as combining their JavaScript files into one. This would reduce HTTP requests and hence improve website performance. You can see a screen shot from YSlow below.
Rules to speed up your website
- Minimize HTTP Requests
- Use a Content Delivery Network
- Add an Expires or a Cache-Control Header
- Gzip Components
- Put Stylesheets at the Top
- Put Scripts at the Bottom
- Avoid CSS Expressions
- Make JavaScript and CSS External
- Reduce DNS Lookups
- Minify JavaScript and CSS
- Avoid Redirects
- Remove Duplicate Scripts
- Configure ETags
- Make Ajax Cacheable
- Flush the Buffer Early
- Use GET for AJAX Requests
- Post-load Components
- Preload Components
- Reduce the Number of DOM Elements
- Split Components Across Domains
- Minimize the Number of iframes
- No 404s
- Reduce Cookie Size
- Use Cookie-free Domains for Components
- Minimize DOM Access
- Develop Smart Event Handlers
- Choose
- over @import
- Avoid Filters
- Optimize Images
- Optimize CSS Sprites
- Don’t Scale Images in HTML
- Make favicon.ico Small and Cacheable
- Keep Components under 25K
- Pack Components into a Multipart Document
- Avoid Empty Image src
The above rules are based on these best practices for speeding up your website.
Download YSlow
YSlow is integrated into Firebug (a must have for all web designers) so you will need to download and install the Firebug add-on first. Once that is installed you can download the YSlow add-on.
Eventually I’ll get around to optimizing the performance of this site (hopefully).
Adham Dannaway
Web Designer and Front End Developer with a passion for web design, coding, blogging, WordPress and chewing gum. Check out my web design portfolio and follow me on Twitter and Facebook!
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