In the styles pane, I notice that sometimes I add a piece of code to my styles and there is a strike across the code, why is this happening and how can I override it?
That happens for a few reasons.
First would be there's a typo in there or an incorrect style input assigned to it. Second BSS doesn't recognize the code you added. This usually means it will still work, just that BSS isn't set up to know what that particular class, id or input is. Third would be that the class is overridden by another class.
If you are sure your class is written correctly, then I would highlight the area on the Overview tree that brings that class up in the Styles window. Now look at the Options pane and change to the first tab which shows lots of settings. In there you can get some clues as to what is actually in effect. Scroll down and you'll see sizes an other attributes. If the attribute is in there that is overriding your class, then you will have the numbers/words that are affecting it and can then more precisely search your CSS files for it.
Sometimes it's a pretty simple thing to do and sometimes not. If anyone else has an easier way, I am open to suggestions as well, but so far this has worked pretty good for me.