Centering an element horizontally within its parent container can be achieved effectively using CSS Flexbox. To do this, you need to apply the `display: flex;` property to the parent container, and then use `justify-content: center;` to align your child element in the center. Here’s a simple code snippet to illustrate this method:

div.parent {
    display: flex;
    justify-content: center;
}

div.child {
    width: 50%; /* Example width */
    height: 100px; /* Example height */
    background-color: lightblue; /* Just for visibility */
}

Additionally, you can also achieve horizontal centering using margin auto. By setting the child element’s width and applying `margin: 0 auto;`, it will automatically center itself within the parent. Note that this method requires that the child element has a defined width. Here’s how you could do it:

div.parent {
    width: 100%; /* Width of the parent */
}

div.child {
    width: 50%; /* Defined width for child */
    margin: 0 auto;
    height: 100px; /* Example height */
    background-color: lightcoral; /* Just for visibility */
}