1）Descendant selectors
http://css.maxdesign.com.au/selectutorial/selectors_descendant.htm

2）You can also specify that only specific HTML elements should be affected by a class.
In the example below, only “p” elements with class=”center” will be center-aligned:
Example
p.center {
text-align: center;
color: red;
}

3）group selectors
To group selectors, separate each selector with a comma.
In the example below we have grouped the selectors from the code above:
Example
h1, h2, p {
text-align: center;
color: red;
}