Align HTML elements horizontally in a div

Try using display:flex.

.header {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
}

<div class="header">
    <input type="button" value="Previous" id="btnPrevious"/>
    <span id="spanStage">Stage 5</span>
    <input type="button" value="Next" id="btnNext"/>
</div>

The "display:flex" style is a good way to make these elements in same line. No matter what kind of element in the div. Especially if the input class is form-control,other solutions like bootstrap, inline-block will not work well.

Example:

<div style="display:flex; flex-direction: row; justify-content: center; align-items: center">
     <input type="button" value="Previous" id="btnPrevious"/>
     <span id="spanStage">Stage 5</span>
     <input type="button" value="Next" id="btnNext"/>
</div>

More detail about flexbox: https://css-tricks.com/snippets/css/a-guide-to-flexbox/

flex-direction: row, column

justify-content: flex-end, center, space-between, space-around

align-items: stretch, flex-start, flex-end, center

Just add text-align: center to your wrapper to set the horizontal alignment of all non-floating/non-positioned children:

div{
    text-align:center;
}

<span> are inline elements by default. Thus you either have to use display:block on them and style them appropriately, or just tweak the parent style a little bit. Since there are no other children than the <span> and the <button>s your best of with this simple solution.

Note that text-align:<value> gets inherited from the parent, so if you want to include something else in your wrapper you should check whether text-align:center is okay for you. Otherwise use text-align:<value> in the specific element, where value is left, right, center or justify.

JSFiddle Demo