CSS

CSS syntax:
1)p {color:red;text-align:center;} --- select(html element) and style
2)#para1
{
text-align:center;
color:red;
} --- is select and style
3).center {text-align:center;} ---class select and style
4)p.center {text-align:center;} --- html element's class select and style

how to use external style sheet: inside html "head" element put "link" element