I am having trouble keeping the rows and columns line up
1) When is desktop mode maximum columns should be three.
When I click on “Cell Three” works fine but when I click on ”Cell Two” it does loose the three column order. 
2) When Tablet maximum columns should be two all the time.
When I click on "Cell Two" works fine but when I click on "Cell Three" it does loose the two column order. 
When Mobile maximum is one column.
3) It does work fine 
I paste the whole code in one file hoping it will be easier to follow, my apologies if is hard to read
Let me know if I am clear with my explanation plz, in advance thank you for your help!
Code:
<!DOCTYPE html>
<!-- include bootstrap -->
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
<style>
/* centered columns styles */
.row-centered {
text-align:center;
}
.col-centered {
display:inline-block;
float:none;
/* reset the text-align */
text-align:left;
/* inline-block space fix */
margin-right:-4px;
vertical-align: top;
}
.col-fixed {
/* custom width */
width:320px;
}
.col-min {
/* custom min width */
min-width:320px;
}
.col-max {
/* custom max width */
max-width:320px;
}
.item {
width:100%;
height:100%;
border:1px solid #cecece;
padding:16px 8px;
background:#ededed;
background:-webkit-gradient(linear, left top, left bottom,color-stop(0%, #f4f4f4), color-stop(100%, #ededed));
background:-moz-linear-gradient(top, #f4f4f4 0%, #ededed 100%);
background:-ms-linear-gradient(top, #f4f4f4 0%, #ededed 100%);
}
/* content styles */
.item {
display:table;
}
.content {
display:table-cell;
vertical-align:middle;
text-align:center;
}
.content:before {
font-family:sans-serif;
font-size:12px;
letter-spacing:1px;
color:#747474;
}
/* Style the tab content */
.tabcontent {
display: none;
padding: 6px 12px;
border-top: none;
}
</style>
<div class="container">
<div class="row row-centered">
<!-- Cell One -->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content">Cell One</div></div></div>
<!-- Cell Two -->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content"><a href="javascript:void(0)" class="tablinks" onclick="openTab(event, 'ImageMngt')">Cell Two</a></div></div></div>
<div id="ImageMngt" class="tabcontent">
<b>Content Cell Two</b><br />
Content Cell Two Content Cell Two Content Cell Two Content Cell Two Content Cell Two Content Cell Two Content Cell Two
</div>
<!-- Cell Three -->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content"><a href="javascript:void(0)" class="tablinks" onclick="openTab(event, 'ImageOff')">Cell Three</a></div></div></div>
<div id="ImageOff" class="tabcontent"><b>Content Three</b><br />
Content Three Content Three Content Three Content Three Content Three Content Three Content Three Content Three Content Three
</div>
<!-- Cell Four-->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content">Cell Four</div></div></div>
<!-- Cell Five-->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content">Cell Five</div></div></div>
<!-- Cell Six -->
<div class="col-xs-6 col-centered col-fixed"><div class="item"><div class="content">Cell Six</div></div></div>
</div>
</div>
<script>
function openTab(evt, tabName) {
var i, tabcontent, tablinks;
tabcontent = document.getElementsByClassName("tabcontent");
for (i = 0; i < tabcontent.length; i++) {
tabcontent[i].style.display = "none";
}
tablinks = document.getElementsByClassName("tablinks");
for (i = 0; i < tablinks.length; i++) {
tablinks[i].className = tablinks[i].className.replace(" active", "");
}
document.getElementById(tabName).style.display = "block";
evt.currentTarget.className += " active";
}
</script>
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