html:not(.webp) .main-header {
    background: url(../images/bg-banner.webp) no-repeat;
    background-size: cover;
    height: 890px;
    background-position: center center;
  }
  html.webp .main-header {
    background: url(../images/bg-banner.png) no-repeat;
    background-size: cover;
    height: 890px;
    background-position: center center;
  }
  html:not(.webp) .our-plan{
    background: url(../images/plain-bg.webp) no-repeat 0 0/cover;
  }
  html.webp .our-plan{
    background: url(../images/plain-bg.jpg) no-repeat 0 0/cover;
  }