There never has been and most likely never will be a universal browser used by everybody whilst surfing the web. Most people love to have the ability to choose from a pool of many things. Nobody enjoys being forced into using one thing because it’s the only thing available or the only thing that works. Nobody wants to be forced into using one browser over another. This is why there are options. There are a handful of different browsers that people are able to freely choose between, and this makes the people very happy. This freedom of choice is rarely seen as an issue by most people. However, this can end up being a rather large issue for website creators who fail to choose a WordPress theme that is best viewed in all of the major browsers. Some people are incredibly loyal to the browser that they use, and if your website isn’t easily viewable on it, they aren’t going to make the effort to change browsers and view it elsewhere.
If you’ve decided on a WordPress theme that only allows for optimal viewing in one or two different browsers, then you’ve made a horrible choice. With an almost infinite supply of WordPress themes that DO allow for cross-browser compatibility, choosing one that isn’t is just absolute nonsense. All this is going to do is lose you page views and fans. If everybody can’t easily enjoy your website, the fans you may have gained will never know what they missed.