The .last class removes the margin-right value from the columns for perfect alignment to the container. Also, a media query specifies that if the screen is smaller than 768px(the width of a tablet screen), display columns one under another. In other words, the code creates responsive columns for Contact Form 7.
Edit the CF7 form and wrap it with divs like <div class="one-half"> ... </div>
Source: https://deliciousthemes.com/contact-form-7-fields-columns/
.one-half,
.one-third {
position: relative;
margin-right: 4%;
float: left;
margin-bottom: 20px;
}
.one-half { width: 48%; }
.one-third { width: 30.66%; }
.last {
margin-right: 0 !important;
clear: right;
}
@media only screen and (max-width: 767px) {
.one-half, .one-third {
width: 100%;
margin-right: 0;
}
}
<div class="one-half">
<label> Your Name (required)
</label>
</div>
<div class="one-half last">
<label> Your Email (required)
[email* your-email] </label>
</div>
<label> Your Message
[textarea your-message] </label>
[submit "Send"]