If the backgroundBlue class in this example has a color attribute ... who coded your Web page to create a CSS class that references a DIV's ID. You may not see a class reference in your DIV ...

The use of classes is also very common when creating webpages. Classes operate in a similar way to element IDs but rather than relating to the id of an individual element, styles for a class can ...

Ryan Boudreaux covers the basics about CSS ... number of ID attributes in the selector and apply the value 0,1,0,0 for each or A=0, B=1, C=0, D=0 or 0,x,0,0. C. Count the number of classes ...