how to reduce the page height using css code example

Example 1: css height property

/* <length> values */
height: 300px;
height: 25em;

/* <percentage> value */
height: 75%;

/* Keyword values */
height: max-content;
height: min-content;
height: fit-content(20em);
height: auto;

/* Global values */
height: inherit;
height: initial;
height: unset;

Example 2: fixed size body html

html {
    position: relative;
    min-width: 1024px;
    min-height: 768px;
    height: 100%;
}
<!-- Remove height 100% if needed fixed height -->