Front-end performance optimizing involves optimizing a website's HTML, CSS, JavaScript, and image files to achieve the fastest possible loading speed. This includes minimizing HTTP requests by combining files, compressing files, optimizing code by removing unused code and errors, leveraging browser caching, and parallelizing downloads across domains. The document outlines nine techniques for front-end optimization, such as optimizing file sizes, reducing download size through compression and caching, and minimizing HTTP requests through file combining and CSS sprites.

1. Front-End Performance Optimizing How to optimize the Front-End to get the maximum loading speed © 2010 by Michael Pehl - http://www.cookielessdomain.com

2. Front-End Performance Optimizing “ Front-End Performance Optimizing”? What is that? Front-End Optimizing is optimizing a website with different techniques to achieve the fastest possible loading speed. In this case only the Front-End counts. The Front-End is the part of the website that is transferred and executed/rendered to the client (browser) and contains at least the following four parts: - HTML code - CSS code - JavaScript code - Image files (optional media files like .swf, .mov, .mp3,...) © 2010 by Michael Pehl - http://www.cookielessdomain.com

3. Front-End Performance Optimizing How does it work? The different parts of the optimizing process are (1-3) : 1. Common HTML Programming Tasks - Avoid HTML errors (W3C Validation) - Delete comments from HTML document 2. Common CSS Programming Tasks - Avoid CSS expressions 3. Optimizing HTML - Optimize the order of styles and scripts - Avoid usage of tables for website design - Avoid usage of inline styles - Avoid usage of inline JavaScript © 2010 by Michael Pehl - http://www.cookielessdomain.com

4. Front-End Performance Optimizing How does it work? The different parts of the optimizing process are (4-6) : 4. Optimizing CSS - Remove unused CSS 5. Optimizing JavaScript - Remove unused JavaScript 6. Minimize HTTP Requests - Combine external CSS - Combine external JavaScript - Use CSS Sprites to reduce the amount of images to download © 2010 by Michael Pehl - http://www.cookielessdomain.com

5. Front-End Performance Optimizing How does it work? The different parts of the optimizing process are (7-9) : 7. Compressing CSS/JavaScript/image files - Minify combined CSS - Minify combined JavaScript - Optimize image file size with tools like Yahoo SmushIt 8. Reduce download size and increment the number of concurrent downloads - Serve static content (CSS/JavaScript/image files) from a cookieless domain - Parallelize downloads across hostnames 9. Server-Side Compression and Browser Caching - Enable compression (mod_gzip/mod_deflate on Apache web server) - Leverage browser caching (mod_expires on Apache web server) - Specify a Vary: Accept-Encoding header (mod_headers on Apache web server) © 2010 by Michael Pehl - http://www.cookielessdomain.com