css media query standard sizes code example

Example 1: media query

@media only screen and (max-width: 600px) {
  body {
    background-color: lightblue;
  }
}

Example 2: media query

@media only screen and (max-width: 800px) {
  body {
    background-color: ; /*your color*/
  }
}

Example 3: screen sizes for css media

<meta name="viewport" content="width=device-width, initial-scale=1" />