✔ 最佳答案
Think of CSS as a file that tells the web browser how your website is to be displayed (layout, colors, font style).
Usually, in your HTML file, you will find tags like <body>, <p>, <a href...>. These tags tell the browser what they are. For example, the <body> tag lets your browser know anything within the <body> and </body> tag is the content it needs to display.
The CSS file lets you define the appearance of the content displayed.
Thus, if you want to add a background to your website, you can add it in the CSS file. I am assuming your background is a solid color now? If yes, you may see something like this in the CSS file:
body {color: #FFFFFF; ....}
All you need to do is add the background image file to the "Body" {}'s.
body {color: #FFFFFF url(location/filename.jpg); ....}
For more information on CSS, check out
http://www.w3schools.com/css/default.asp and
http://www.cssbasics.com/
