I think of websites as living, organic entities. They rarely stay the same, a good site should be regularly updated with fresh content, new ideas and there are a lot of external factors than can effect a them.
The browsers we use are constantly changing, every four weeks a new version of Chrome is released, every six Firefox gets updated and Internet Explorer 9 and 10 are a massive overhaul of Microsoft’s offering potentially breaking backwards compatibility. Additionally, more and more people are using mobile phones or on tablets and these new form factors and methods of interaction bring new problems and challenges to deal with. Under-the-hood the server the website runs on gets updated with security patches and new versions of software, or hardware fails and needs to be replaced.
All of these factors and many more combine to make websites potentially very unstable so it’s no surprise that from time-to-time errors occur, be they a bug in the website itself, Google updating the way a feature in Chrome works or a change in third party code meaning the site fails to correctly load. So how do we keep track of these potential pitfalls and respond to them?