我正在使用Twitter Bootstrap制作一个表单,但是很难把按钮居中。它包含在一个具有7个间距的span的div内。以下是HTML代码,按钮位于底部。请问如何将其居中显示?
<div class="form span7">
<div id="get-started">
<div id="form-intro">
<strong><h1>1. Get Started: Some basics</h1></strong>
</div>
<form class="form-horizontal">
<div class="control-group">
<label class="control-label" for="inputSaving">What are you saving for?</label>
<div class="controls">
<input class="span4" type="text" id="inputSaving" placeholder="e.g. Swimming Lessons, Birthday Party, College Fund, etc.">
</div>
</div>
<div class="control-group">
<label class="control-label" for="description">Add a short description</label>
<div class="controls">
<textarea class="span4" id="description" rows="4" placeholder="Describe in your own words the saving goal for this piggybank"></textarea>
</div>
</div>
<div class="control-group">
<label class="control-label" for="categoryselect">Choose a Category</label>
<div class="controls">
<select class="span4" id="categoryselect">
<!-- Add some CSS and JS to make a placeholder value-->
<option value="Kittens">Kittens</option>
<option value="Keyboard Cat">Keyboard Cat</option>
<option value="Twitter Bird">Twitter Bird</option>
</select>
</div>
</div>
<div class="control-group">
<label class="control-label" for="imageselect">Choose an image</label>
<div class="controls span4">
<img src="piggyimage.png" id="imageselect" alt="image-select" />
</div>
</div>
<div class="control-group">
<label class="control-label" for="goal">Your Saving Goal</label>
<div class="controls">
<input type="text" class="span4" id="goal" placeholder="$1337">
</div>
</div>
<button class="btn btn-large btn-primary" type="button">Submit</button>
</form>
</div>
</div>
<div class="btn-group btn-group-lg span7">
一起使用! - TOPKAT