Have you already got a web site, but found that it isn't performing as well as you'd like? Perhaps the problems lie as much in the construction as the content.
Technical issues with the way a site has been implemented can mean that the content is not displayed as intended in some browsers, so some of your visitors (and the search engines) may see a much less appealing site than you do. In the worst case we have come across, a site was only displayed properly in two (older) versions of Internet Explorer and in the latest IE and four other browsers tested, it just showed a black page with a few subheadings that looked like links but didn't do anything when clicked on.
We can use tools to check for these 'browser compatibility issues' and also for problems in the coding of the pages.
If you want to improve and build on your existing site, rather than totally replacing it, this can be an important first step in the tasks undertaken to improve your visitors' experience and the ranking in search engines.