With the increasing pixel density of many screens, the appearance of text is seeming smaller and smaller to viewers. Many people increase the size, sometimes by adding a style to the page. If you're using values, your content will remain un-viewable for these people. Also, people are viewing web pages on more and more different sizes and shapes of devices. Responsive web designs can ensure that your site will look great wherever it's seen, but not if you're using pixels for font sizes and line spacings. |