Issues with styling content within a post

ok so I’m a little tired tonight and trying to put together a post that is using classes in CSS. In other words I have a line that was once using inline styling like this…

<span style="font-size:500%">W</span>

…and I have tried to put this into my main styling as it will be a common thing in my posts to have a large capitalized first letter. Now I have tried to call this style by using a class as follows…

<span class="fl">W</span>

Its not working…anyone have any clue as to why? I have tried googling here to no result…maybe I need to work on my googlefu.