40-60% of daily visitors to your site come in with an empty browser cache. Making your page fast for these first time visitors is key to a better user experience. Both web browsers and web servers allow for caching. These caches store previous requests on the browser or server; requests such as images, web pages, CSS/JS files and other data such as cookies. By storing these responses, bandwidth use is reduced, helping to improve a website's performance. Caching is often best used on assets that seldom change, such as CSS and JavaScript files. You can set an expiry date for when an asset should change, effectively telling the browser or server to pull in a fresh copy of your assets.
Steve Krug's first law of usability states the average website user's perspective succinctly - "Don't make me think!". The key concept in question here is cognitive...
