Two major obstacles stand in the way of making a site effective: ego (“sorry, the CEO insists that the background be lime green”), and design-by-committee (“let’s take a vote to see what colour the background should be…)

Even if the project is outsourced, you’re still relying on the taste and skills of the designer to determine this crucial aspect of your business.

Concentrating on hard data can remove that human factor. Lovefilm distributes rental movies to subscribers through the post, and its success depends almost entirely on its website allowing customers to browse and order films.

Since they started using testing company Optimost (recently bought by large web content management firm Interwoven), Lovefilm has increased its conversion rate by 10 per cent.

‘You can see what is and isn’t working,’ says Craig Sullivan, product manager, digital and usability. ‘We sliced up the homepage into regions and came up with 192 variants to put there – a few crazy ideas, along with some sensible ones. We found that by removing prices from our home page we increased conversion by 5.5 per cent. It was completely counter-intuitive.’

Sullivan is an enthusiastic advocate of the technology, having sat through numerous unproductive design meetings. ‘Testing removes the incessant arguments and whining from the design process. I was losing the will to live in our meetings – we once spent half an hour discussing whether a link should have an underline.’