Something as simple as placing your navigation bar beneath your main header is susceptible ... are incorrect ordering in HTML files or incorrect usage of the "float" CSS command.

Use CSS code to style your site headers with borders and other design elements. HTML and CSS use a box model, which means that page elements include margins, padding, background colors and ...

jsFiddle is the perfect solution; it provides a custom environment (based on user selections) to test (or fiddle with) your JavaScript, HTML, and CSS code ... to use is as simple as loading ...