[css] hide div tag on mobile view only?

You can be guided by this example. On your css file:

.deskContent {
    background-image: url(../img/big-pic.png);
    width: 100%;
    height: 400px;
    background-repeat: no-repeat;
    background-size: contain; 
}

.phoneContent {
    background-image: url(../img/small-pic.png);
    width: 100%;
    height: 100px;
    background-repeat: no-repeat;
    background-size: contain;
}

@media all and (max-width: 959px) {
    .deskContent {display:block;}
    .phoneContent {display:none;}
}

@media all and (max-width: 479px) {
    .deskContent {display:none;}
    .phoneContent {display:block;}
}

On your html file:

<div class="deskContent">Content for desktop</div>
<div class="phoneContent">Content for mobile</div>