Why hidden input is affecting my layout? LF Explanation

Is because you have a css rule (in bootstrap.min.css file) that match the firs-child element (but only if has a class*="span") inside the default_shipping_box div.

.row-fluid [class*="span"]:first-child {margin-left: 0;}

So, if you put your hidden input inside the div#default_shipping_box and before the first span, then that rule is not styling the div.span1 and thats why your template is been afected.

You can fixed adding a simple css rule to the same file...

.row-fluid .span1{margin-left:0 !important;}

The important, is because you have more files who overite this rule (ex. in bootstrap-responsive.min.css)

Good luck, and i hope it helpscheers,Gmo.-

EDIT:Too slow XD.Answered while writing ... I agree with the reason explained above.

Using Google Chrome's Inspest Plugin, when you move the input this class:

.row-fluid [class*="span"]:first-child {     margin-left: 0;}

Gets removed.

This is because in this:

<div id="shipping_box" class="formSep well">    <div id="default_shipping_box" class="shipping_box row-fluid">        <input type="hidden" name="tracking_id" value="" />        <div class="span1">        </div>    </div></div>

This : <div class="span1"> is not the first child, this: <input type="hidden" name="tracking_id" value="" /> is.

and in your CSS this is that default class for [class*="span"] is:

[class*="span"] {    float: left;    margin-left: 30px;}

So use this for example :

.row-fluid .span1 {    margin-left:0 !important;}

Hope this helps.

Bootstrap has some CSS that will set the left-margin of the first of the child to 0, if the class contains span:

.row-fluid [class*="span"]:first-child {    margin-left: 0;  }

When the hidden input is put above the first span div, the above margin-left: 0; property will not be applied.

The following image shows that when the hidden input is before, then the first span class has a left-margin.

This shows that when the hidden input is after the div, that there is no left-margin.

EDIT: I seem to have a been beaten twice, while I was getting the screenshots to illustrate the difference!