How to center a div with Bootstrap2?

http://twitter.github.com/bootstrap/scaffolding.html

I tried like all combinations:

<div class="row">
  <div class="span7 offset5"> box </div>
</div>

or

<div class="container">
  <div class="row">
    <div class="span7 offset5"> box </div>
  </div>  
</div>

changed span and offset numbers...

But I cant get a simple box perfectly centered on a page :(

I just want a 6-column-wide box centered...

did it with

<div class="container">
  <div class="row" id="login-container">
    <div class="span8 offset2">
       box
    </div>
  </div>
</div>

But the box is too wide, is there any way I can do it with span7 ?

span7 offset2 gives extra padding to the left span7 offset3 extra padding to the right...

Bootstrap's spans are floated to the left. All it takes to center them is override this behavior. I do this by adding this to my stylesheet:

.center {
     float: none;
     margin-left: auto;
     margin-right: auto;
}

If you have this class defined, just add it to the span and you're good to go.

<div class="span7 center"> box </div>

Note that this custom center class must be defined after the bootstrap css. You could use !important but that isn't recommended.

besides shrinking the div itself to the size you want, by reducing span size like so... class="span6 offset3", class="span4 offset4", etc... something as simple as style="text-align: center" on the div could have the effect you're looking for

you can't use span7 with any set offset and get the span centered on the page (Because total spans = 12)

Bootstrap3 has the .center-block class that you can use. It is defined as

.center-block {
  display: block;
  margin-left: auto;
  margin-right: auto;
}

Documentation here.