I have the following setup:
<!-- content goes here -->
What I'm currently doing to center stuff horizontally is this:
<div class="span12" style="float:right">
<div class="span7" style="float:left;">
<!-- centered stuff goes here-->
This seems like a lot of extra markup. Is there another class I could use to simply horizontally align a spanX within a container?
If you want to center something within any element, you can assign special styles to it: margin: 0 auto;. If you want to center something within .row you can use the .offset* classes in the grid system to indent a column by some n number of columns.
margin: 0 auto;
Here's a nice sample of centering using this method: http://jsfiddle.net/rfkrocktk/hcQ48/