Best practice to add vertical space?

I’ve got some funky vertical spacing on a Twentytwelve site I’m working on now, so I’d like to add some vertical space below some items. I’ve found that in some circumstances, I can add a <div> statement like

<div style="float: left; width: auto; height: 10px;"></div>

to get what I want, but most times this doesn’t work. Something in the CSS is overwriting the inline statement.

So I wonder — what’s the best way to create vertical spacing in Twentytwelve? I suppose I could use a transparent .GIF, but then I couldn’t have any styling of image borders. Thanks for your help…