Here is the Answer
CSS
#outer
{
width:100%;
text-align: center;
}
.inner
{
display: inline-block;
}
HTML
<div id="outer">
<div class="inner"><button type="submit" class="msgBtn" onClick="return false;" >Save</button></div>
<div class="inner"><button type="submit" class="msgBtn2" onClick="return false;">Publish</button></div>
<div class="inner"><button class="msgBtnBack">Back</button></div>
</div>