Site speed is one of the most important elements in providing a good online user experience as nobody wants to sit around waiting for pages to load.
In fact research has shown that a one second delay in load time can cause 7% loss in customer conversions.
But a new report from Radware suggests that despite the effort that businesses put into ensuring a fast load time, average site speeds are actually getting slower.
The study shows that in spring 2012 the median page took 6.79 seconds to load, but this has now dropped to 7.72 seconds, a slowdown of 13.7%.
Among the top 500 leading retail websites, as ranked by Alexa.com, Ikea was found to have the fastest full load time at just 1.85 seconds followed by AbeBooks (2.06 seconds) and Pixmania (2.20 seconds).
10 fastest sites (full load time)
However the report also measures sites based on their 'time to interact' (TTI), which is defined as the point at which a page displays its primary interactive content (e.g., feature banners with functional call-to-action buttons).
Using this metric, Adpost actually clocks the fastest time at 0.7 seconds followed closely by Groupon and AbeBooks (both 0.8 seconds).
To give an idea of the distinction between the two metrics, Netflix has a TTI of 1.4 seconds but a full load time of 4.37 seconds, while LivingSocial has a TTI of two seconds and a full load time of 8.58 seconds.
According to the report, TTI is actually seen as a more relevant metric than the full load time as it's the point at which visitors can begin to use the site.
Among the top 100 sites tested the median TTI was 4.9 seconds. Only 8% of the top 100 sites had a TTI below two seconds, while 9% had a TTI of eight or more seconds.
In order to reduce the TTI, Radware suggests taking the following action:
1. Defer rendering 'below the fold' content
Page speed can be improved by delaying loading and rendering any content that appears below the initial visibility area.
To eliminate the need to reflow content after the remainder of the page is loaded, replace images initially with placeholder <img> tags that specify the correct height and width.
2. Ensure that interactive features are optimised to load early and quickly
The report suggests making sure that homepage elements such as carousels are optimised to be among the first elements to load, as on Staples.com the carousel didn't begin loading until the two second mark then took a further three seconds to load fully.
However a better idea might be to remove slow elements that also do little to improve the user experience. We've previously investigated the use of carousels on ecommerce sites, and found there's some doubt over whether they're worth the effort.
3. Defer loading and executing non-essential scripts
Many script libraries aren't needed until after a page has finished rendering. Downloading and parsing these scripts can safely be deferred until after the onload event.
For example, scripts that support interactive user behaviour, such as drag and drop, can't possibly be called before the user has even seen the page. The same logic also applies to script execution.
Therefore it's a good idea to defer as much as possible until after onload instead of needlessly holding up the initial rendering of the important visible content on the page.