horizontally is to set the display:table,margin:0 auto, code for child elements as follows
<style>
.parent_3 {
}
.child_3 {
display: table;
margin: 0 auto;
}
</style>
<section class="parent parent_3">
<article class="child child_3"></article>
</section>the effect of the browser is shown in the figure
both table and block can declare block-level elements, so why can"t block achieve this effect?
what are the performance characteristics of elements when display is table?