Quick CSS Page Margins ?uestion

**hey! **
i’ve got a linked style sheet thats not acting the way i want it too. i want to set all the page marigins to zero and added the following code to my style sheet:

 margin-top: 0px; 
 margin-bottom: 0px; 
 margin-left: 0px; 
 margin-right: 0px 

 background: yellow; 
 font-family: courier 


now… the < p > styles are working just fine… so i must be doing something wrong, or using the wrong code to effect the page margins. what do i need to do differently? **thanks! :block: **