.design-block{
    float: left;
    margin-bottom: 10px;
    width: 49%;
}
.design-block_first{
    margin-right: 2%;
}

@media screen and (max-width: 750px) {
    .design-block{
        float: none;
        width: auto;
    }
    .design-block_first{
        margin: 0;
    }
}