When in doubt, view the page in FireBug. It will strike out the classes that are overridden and show the order which they are applied in the page.
Also note that inline styles will override those declared in an external stylesheet. If you want to break the cascading chain af applicability, you can use the !important declaration as in
p {margin: 10px 5px 0 10px !important}
This will cause the !important declration to override others regardless of position. Some see it as bad practice, but it can come in handy if used judiciously.
