I'm new to Bootstrap and I came across this issue. 

```
<div class="container row">
    <div id="page" class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1">
        <div id="header"></div>

        <div id="article"></div>

        <div id="footer"></div>

    </div>
    <div class="col-lg-2 col-md-1"></div>

```

In boostrap documentation it shows that I dont have to use the last div.
doc: `<div class="row">
 <div class="col-md-6 col-md-offset-3">.col-md-6 .col-md-offset-3</div>
</div>`

6 + 3 = 9. There are 3 col missing. I just want to make sure I understood this well before progressing into more details.
IF there are `col` missing inside a `row` will `row` automatically add them?
Or will I have some sort of a surprise bug at the long run.

I was using the 1200px grid system before. and I always had to add the the cols in correct order and correct numbers.