space
The background image is displayed in its original size.
background-size: 300px 100px:
C
C
Here, the background image is set to 300px wide and100px 
high.
The background image is displayed in its original size.
background-size: 300px 100px:
Here, the background image is set to 300px wide and100px high.
Note: The background-size property is not supported in Internet Explorer 8 and earlier versions.