Fixed .spanX selector (*= instead of ^=)

`[class^="span"]` will only match elements with a class attribute that begins with "span", meaning it won't work if spanX isn't the first class. This caused me some confusion when I had an element with multiple classes and couldn't figure out why it wasn't floating left. Changing the selector to `[class*="span"]` will match any elements that have "span" in the class attribute.