Bootstrap row layout - html

Question

I'm trying to create a form that will appear in a modal window and I have the form looking exactly what I want. Here's my HTML (only showing the first row because I believe the right solution will apply to all my rows)
<div class="container">
<div class="row">
<div class="col-sm-1"> </div>
<div class="col-sm-8">
<form action="#" method="post">
<fieldset>
<legend style="width: 80%">Base Information</legend>
<div class='row'>
<div class='col-sm-5'>
<div class='form-group'>
<label for="user_firstname">First name</label>
<input class="form-control input-sm" id="user_firstname" name="user[firstname]" required="true" size="30" type="text" />
</div>
</div>
<div class='col-sm-5'>
<div class='form-group'>
<label for="user_lastname">Last name</label>
<input class="form-control input-sm" id="user_lastname" name="user[lastname]" required="true" size="30" type="text" />
</div>
</div>
<div class="col-sm-2"> </div>
</div>
</fieldset>
</form>
</div>
</div>
</div>
The problem I'm facing is that I'm currently viewing this using Chrome and when I horizontally resize the browser window to less than 760 pixels, all the form elements are stacked on top of each other.
As you can see there's a lot of spacing to the right I'm trying to get rid of.
Does anyone have any suggestions on how I can eliminate the padding on the right?

Answer 1

col-xs instead of col-sm would help with the breakpoint issue. You also seem to have empty space on the right because you specified two columns of empty space <div class="col-sm-2"> </div>. Bootstrap's grid system is based uon 12 columns per row, so the two column spanning div would be occuping space.

Answer 2

Bootstrap suggests 12 columns. Your layout uses only 9 of them:
<div class="col-sm-1"> </div>
<div class="col-sm-8">
...
</div>
You can use col-sm-10 col-sm-offset-1 instead of col-sm-8, <div class="col-sm-1"> </div> and <div class="col-sm-2"> </div> (offsetting columns):
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<div class="container">
<div class="row">
<div class="col-sm-10 col-sm-offset-1">
<form action="#" method="post">
<fieldset>
<legend>Base Information</legend>
<div class="row">
<div class="col-sm-6">
<div class="form-group">
<label for="user_firstname">First name</label>
<input class="form-control input-sm" id="user_firstname" name="user[firstname]" required="true" size="30" type="text" />
</div>
</div>
<div class="col-sm-6">
<div class="form-group">
<label for="user_lastname">Last name</label>
<input class="form-control input-sm" id="user_lastname" name="user[lastname]" required="true" size="30" type="text" />
</div>
</div>
</div>
</fieldset>
</form>
</div>
</div>
</div>