Client edited page that broke code - how to fix? Dawn Theme

My client updated her page this morning, which broke the code for having the text appear in two rows. Additionally, her signature was at the bottom.

I’ve tried adding the below code to both the base.css and page html - but it just is not working. Am I missing something? Additionally, how can I embed the signature link at the bottom?

.one-half-column-left {
width:48%;
float:left;
}

.one-half-column-right {
width:48%;
float:right;
}

@media only screen and (max-width: 600px) {
.one-half-column-left, .one-half-column-right, 
.one-third-column, .one-third-column-last {
float:none;
width:100%;
margin-right:0;
}
}
<div class="one-half-column-left">
<p>Insert the content for the left column here.</p>
</div>
<div class="one-half-column-right">
<p>Insert the content for the right column here.</p>
</div>
<br style="clear:both;" />

Appreciate the help!

Hi @Dallas_Taylor

If this was appearing correctly previously, can you roll back to a previous version?

Are you still seeing this issue @Dallas_Taylor ?