I don’t see how it affected the front page. The front page already had code that set the margin-top to 0 –
.front-page .site-container .site-inner {
margin-top: 0;
max-width: 100%;
overflow: hidden;
}
So no matter what margin you add to the main .site-inner
the code above overrides it on the homepage since it’s not needed due to the widgets.
The Responsive section for this is currently on line 2434 –
.site-inner {
margin-top: 40px;
}