FrontEnd Optimization

Minimize HTTP Requests
Put Stylesheets at the Top
Put Scripts at the Bottom
Avoid CSS Expressions
Make JavaScript and CSS External
Minify JavaScript and CSS
Avoid Redirects
Remove Duplicate Scripts
Make Ajax Cacheable
Use GET for AJAX Requests
Post-load Components
Pre-load Components
Reduce the Number of DOM Elements
Minimize the Number of iframes
No 404s
Minimize DOM Access
Develop Smart Event Handlers
Choose over @import
Optimize Images
Optimize CSS Sprites
Don’t Scale Images in HTML
Keep Components under 25K
Pack Components into a Multipart Document
Avoid Empty Image src
Reduce DNS Lookups
Avoid Filters

Backend Optimization

Use a Content Delivery Network
Add an Expires or a Cache-Control Header
Gzip Components (Reduces size to 70%).
Configure ETags
Flush the Buffer Early
Split Components Across Domains
Reduce Cookie Size
Use Cookie-free Domains for Components
Make favicon.ico Small and Cacheable | | | | Yahoo Developer Network

window.onLoad=function(){alert(“Hello, Kumar!”);}; //JavaScript
jQuery(document).ready(function(){alert(“Hello, Kumar!”);}); //jQuery