We use <a> element to add a link to other web.

　　This is exmaple about text-only links:

　　　　<a href="http://www.mamicode.com/www.google.com" target= "_blank">Google</a>

　　And this is exmaple about picture links:

　　　　<a href="http://www.mamicode.com/www.google.com" target= "_blank"><img src="http://www.mamicode.com/#" alt ="google"/></a>

【codecademy summary】html+css links