display line box flexible css code example

Example 1: make the first item at the very top of the screen

.fixedElement {
    position:fixed;
    top:0;
    width:100%;
    z-index:100;
}

Example 2: flexbox css

.container {
  align-content: flex-start | flex-end | center | space-between | space-around | space-evenly | stretch | start | end | baseline | first baseline | last baseline + ... safe | unsafe;
}