The fact that we can do something doesn’t mean that we should do it. There are many human habits that are not good for us, but we do them anyway. In this case i am talking about the size of fonts on web pages. Almost without exception my clients predictably ask me to reduce the font size on their sites, after i have taken the trouble to conform them to best usability practices.
In general what we have here is a battle between what people perceive as looking good (small fonts) and what they tell usability experts in study after study is easiest to read (larger fonts). So it boils down to an issue of looks versus functionality.
Most website owners try to take steps to encourage visitors to stay on their site. This is why page loading speed has caught the interest of so many. It is the first place that usability factors come into play.
The second place where usability matters is in the adaptability of a website to different screen sizes and browser capabilities on a wide variety of devices. Does the site display properly on a phone? Does it work without Flash? If your site fails in usability at this point, the user will most likely abandon their visit and go elsewere.
Once the page has loaded, if they are still with you, the next task in keeping their attention is to answer their primary question: — what is this site about and does it have what i am looking for? If they cannot get an answer to this, or it is not what they are looking for, then you have lost them. This is the point at which they start to interact with your content – to answer their first question. But what happens if they cannot quickly take in your basic message because they cannot easily read it? Again, they will simply leave.