Enter a reason for deleting this comment
It would help to know what an ID selector is. Can someone explain.
the ID select is just one of CSS's many selectors. A selector in CSS is actually a pattern that is used to select the element you're wanting the style applied too, for example ID has #id and class has .class. The part before the word being the key part of that, the words 'id' and 'class' could be anything.
If you want to read more I suggest taking a look at W3Schools page on CSS Selectors: http://www.w3schools.com/cssref/css_selectors.asp