Just like the newswpapers, web sites have an ‘above the fold’ zone where all the important stuff goes – the first screen shot the visitor sees.

Getting ‘above the fold’ speed up to scratch is important for a whole stack of reasons ...

• Bounce rate – visitors want to quickly find out if they are in the right place - are you what they are looking for? They get bored easily and go.
• Conversion - eg. you’ve got promotions you want them signing up for or getting visitors registered, Getting this stuff above the fold HUGELY increases conversion.
• User experience – if you don’t optimise ‘above the fold’ all the data downloads at the same time – images off the page will be slowing down the top half and causing unhelpful frustration.

Measurement ...

The amount of your site visible to each visitor to your site will depend on their screen resolution and whether they have their browser window maximized or not. To see how much of your site is visible to a typical visitor see Google Labs browsersize tool

To measure your bounce rate and conversion, check out Web Analytics tools such as Google Analytics or Omniture. However if you are looking for an analytics tool which also measures the actual user experience of the visitors to your site then I'd recommend you take a look at our own WebTuna.

Lazy image loading

On longer web pages containing many large images, Lazy Image Loading will make the page load much faster. The browser will be in ready state after loading only the visible images. The images lower down the page will be loaded by JavaScript ‘just-in-time’ if the user scrolls to them.

In some cases it can also reduce the server load and network bandwidth too since, if the user doesn’t scroll down, those images are never requested from the server.