Hi,
If you don't know why you are using them then don't use either.
The base CSS is just a reset similiar to
Code:
* {margin: 0 ; padding: 0;}
But it explicitly sets default values for each element and doesn't have the problems that the above method does (like losing the depressed look of buttons in forms).
The grid is similar to the 'blueprint' framework - it makes it simple to create grid like layouts from your elements using the predefined classes - without needing to know about CSS positioning and floats etc..
It depends what you purpose in using the frameworks is, if you are wanting to learn about CSS this is not what you want to use, your better to start from scratch if you really want to learn about CSS rules and properties.
But if you just want to be able to create layouts then you could use these frameworks. The reset and the fonts CSS files are good to include though - they will give you a consistent default in all browsers so there will be more consistency.
Hope it helps
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