Cannot use FBML in css style block

I'm learning a lot about facebook right now -- especially that there are not a lot of good resources whe you want to do more complex coding with it. The tutorials mostly skim the surface of the easiest integration -- or provide you wiht code that you have to deconstruct. Even the OReilly "Essential" book is a joke--it give a few pages of intro and then just provides the API in book form.

In any event, here is a css tip: you cannot use FBML is a style block. For instance, if you have a div like this:

<div class="content"></div>

and you define the style in a block:

<style>
.content{
width:400px;
}
</style>

you can't use FBML to change the property based on something like the width of the profile box it appears in:

<style>
.content{
<fb:wide> width:400px;</fb:wide>
<fb:narrow> width:100px;</fb:narrow>
}
</style>

Instead, you'll need to use inline styles --or enclose the tag itself in the fbml code:

<fb:wide> <div id="content" style="width:400px"></fb:wide>
<fb:narrow> <div id="content" style="width:100px"></fb:narrow>