Article in English: Though the <center> tag is obsolete, you can create a new element to add to any part of a page to center text within its boundaries. If you don't have a separate file for your CSS, you'll find the styles at the top of the HTML file between the  "<style>" and  "</style>" tags.  If you don't already have <style> and </style> tags, add them directly below <body>  at the top of the file like this:  <!DOCTYPE html> <html> <body> <style>  </style> The <div> tag will tell your HTML document to reference a specified section of text, so you'll create a class for that tag. Type the following into the space between the "style" tags, making sure to press ↵ Enter twice after the first line:  div.a {  } Type text-align: center; into the space between the two curly brackets in the div.a section. The header should now look like this:  <!DOCTYPE html> <html> <body> <style> div.a { 	text-align: center; } </style> You'll do this by placing the <div class="a"> tag above the text you want to center and closing with a </div> tag below the text you want to center. For example, to center a header and its paragraph text, you would enter the following:  <div class="a">  <h1>Welcome to My Website</h1> <p>This website is primarily for the purpose of providing information about things.</p>  </div> To center another element (e.g., content between tags like <p></p> and <h2></h2>), type <div class="a"> before the item, and  </div> after it. Since you already have "div.a" specified as the centering command, this will center the text just like it did before:  <style> div.a { 	text-align: center; } </style>   <div class="a">  <h2>Donations Welcome</h2> <p>please</p>  </div>

Summary in Vietnamese:
Mở tập tin chứa phong cách CSS. Tạo lớp căn giữa văn bản. Thêm thuộc tính text-align. Thêm thẻ div thích hợp vào văn bản cần được căn giữa. Sử dụng thẻ div.a để căn giữa những vùng khác.