You're confusing my reference to DIVitis with my comment about layout in the HTML. The examples providied by the Bootstrap page are stuffed with unnecessary DIVs. I'm a web developer, so I know that DIVs exists to provide containers which add no semantic meaning to the page. But putting classes into your HTML which say class='row' or class='leftcolumn' means that you can't just change the CSS in order to change the layout - which is the whole purpose of CSS in the first place. All grid systems suffer from this weakness.
Consider this example based on the Bootstrap examples - you have three boxes containing stuff within a DIV with a class of 'row'. At some point in the future you decide to turn this into a column. Easy to do in the CSS - just change the width to the with of one item, and they'll stack on top of each other. BUT, now you have a column labelled 'row' in your HTML. This is a fairly simple to rectify example, but this problem is pervasive in grid systems.
Consider this example based on the Bootstrap examples - you have three boxes containing stuff within a DIV with a class of 'row'. At some point in the future you decide to turn this into a column. Easy to do in the CSS - just change the width to the with of one item, and they'll stack on top of each other. BUT, now you have a column labelled 'row' in your HTML. This is a fairly simple to rectify example, but this problem is pervasive in grid systems.