You have a closing </div>
tag immediately after opening the #gridRow
div, which means the .gridX
elements are not children of that div. If you remove the extra closing tag it works fine:
<div id="gridRow">
<div class="gridC-R45"><div><span>COLA</span></div></div>
<div class="gridC-R45"><div><span>COLB</span></div></div>
<div class="gridC-R45"><div><span>COLC</span></div></div>
<div class="gridC-R45"><div><span>COLD</span></div></div>
</div>
Assuming you aren't already I would suggest using a text editor with syntax highlighting. It makes it 99.9% impossible to make mistakes like this.