Read this tip to make your life smarter, better, faster and wiser. LifeTips is the place to go when you need to know about Navigation and other Html topics.
Since you're viewing this page, I know that you've got a web browser. But is the browser that you're using exactly the same as what your site's visitors will be using? Maybe, maybe not.
One of the first things you need to do, as a webpage developer, is find as many different browsers as possible. I'm not implying that you need to use them yourself to surf the web, but when you test your pages you should test with a wide variety of browsers. Once you see what the output will be in different browsers you can tweak your HTML code to be compatible with as many as possible while still delivering the look and feel you intended.