how to add rectangle in html code example

Example 1: how to write inside a rectangles in html

<div style="width:500px;height:100px;border:1px solid #000;">This is a rectangle!</div>

Example 2: html content in rectangle

<style>
.rectangle{
padding-top: 40px;
  width:100px;
  height:100px;
  border:1px solid #000; 
  position: relative;
  text-align: center;
}
</style>

<div class="rectangle">Hello world!</div>