Generate CSS sprite sheets
Group small images (e.g. the website’s interface images) in one larger image called a sprite sheet
This process significantly reduces the number of HTTP requests. There are several free online services for generating sprite sheets (Project Fondue’s CSS Sprite Generator, CSSsprites.com and SpriteMe.org).
Use local variables
When you call a global variable in JavaScript, the interpreter must check that:
- it exists in the current scope, in the scope above, etc.
- the variable has a value
- and more
To avoid all these checks, it is often possible to make useful variables local by transforming them into routine arguments. This process saves CPU time.