How to speed up your web site/application

In my recent experience I have faced some performance issues one of them is web application becomes very much slow. To identify this problem I have searched over the net and I have found a lots of topics.

Now I want to share some of the topics with you in summarized way:

1.Minimize HTTP Requests
2.Use a Content Delivery Network
3.Add an Expires or a Cache-Control Header
4.Gzip Components
5.Put Stylesheets at the Top
6.Put Scripts at the Bottom
7.Avoid CSS Expressions
8.Make JavaScript and CSS External
9.Reduce DNS Lookups
10.Minify JavaScript and CSS
11.Avoid Redirects
12.Remove Duplicate Scripts
13.Configure ETags
14.Make Ajax Cacheable
15.Flush the Buffer Early
16.Use GET for AJAX Requests
17.Post-load Components
18.Preload Components
19.Reduce the Number of DOM Elements
20.Split Components Across Domains
21.Minimize the Number of iframes
22.No 404s
23.Reduce Cookie Size
24.Use Cookie-free Domains for Components
25.Minimize DOM Access
26.Develop Smart Event Handlers
27.Choose over @import
28.Avoid Filters
29.Optimize Images
30.Optimize CSS Sprites
31.Don't Scale Images in HTML
32.Make favicon.ico Small and Cacheable
33.Keep Components under 25K
34.Pack Components into a Multipart Document
35.Enable HTTP Keep-Alives
36.Adjust Connection Timeouts
37.Enable HTTP Compression