[dangrossman]

You can line up every element in your design without figuring out and writing widths and margins for every element by hand. You just assign one of the provided class names and you automatically get the desired result.

[tstegart]

So how do you find what to adjust in the CSS? Just read through it until you figure it out? For example, if I wanted to make four columns instead of three?

[dangrossman]

You don't have to edit the CSS at all. You don't even have to open the file, ever, to use Bootstrap. Just link it in the head of your document like any stylesheet and use the class names from the documentation.

Want something on your page to be 3 columns wide? <div class="span3">...</div>

Want to make it 4 columns wide instead? <div class="span4">...</div>

[tstegart]

You sirs, are both awesome. I think I need to do more research into all of this and find a good how-to guide because if I didn't know how to do the above, I probably shouldn't be doing it until I know more. I've been down that path before and it leads only to frustration when I realize I know no idea what I'm doing :)

[tptacek]

In Haml:

  .span3
    = render :partial => "col1"
  .span3
    = render :partial => "col2"
  .span3
    = render :partial => "col3"
  .span3
    = render :partial => "col4"

Or, to do 3-col:

  .span4
    = render :partial => "col1"
  .span4
    = render :partial => "col2"
  .span4
    = render :partial => "col3"

Nothing in the partial needs to especially care about the grid (as long as its simple) --- but if it wanted to, it could nest columns.

[aaronbrethorst]

or better yet, you have semantically named elements and assign them column values in your .less file:

    #sidebar {
      .makeColumn(4);
    }
    #main_pane {
      .makeColumn(8);
    }

    #sidebar
      = render :partial => 'common/sidebar'
    #main_pane
      = yield