I've seen lately a lot of discussions about this new concept called oocss and I was wondering if it is a bad practice to wrap your main tags in divs only for styling/page layout purposes. I'm asking this because I see some frameworks like Twitter Bootstrap use such a method. What are the implications of such a markup from a semantic and accessibility point of view? For example: <div class="container"> <div class="row"> <div class="span4"> <nav class="nav">...</nav> </div> <div class="span8"> <a href="#" class="btn btn-large">...</a> </div> </div> </div> instead of <div class="menu"> <nav class="nav">...</nav> <a href="#" class="bttn">...</a> </div>