The normalize.css scripts is used alongside HTML5 so that browsers render elements consistently and according to current standards. It will precisely normalize only necessary styles. It will normalize the different styles of each browser.
Semantics is the study of meanings of words and prhrases in a language. Thus, semantic markup is a way of writing and structuring HTML so that it aligns with the meaning, or semantics, of the content rather than the appearance. It requires an understanding of hierarchy of the content and how it will be read by users and machines.
The image above is 600 pixels wide, 450 pixels tall, and takes up 219 KB on the disk.