<div> and <span> use to specify a style or binding script for the content. Although most HTML elements can set style information through the Style property, many HTML elements have their own default styles that might mix and even conflict with style-defined styles that we don't want to see. such as: <strong style = "color:red" >i am strong!</strong>. Unlike other HTML elements,,<div> and <span> do not have a default display style. So you can use them to specify the style.
(1) <div> (division) is a block-level element that can contain paragraphs, headings, tables, and even chapters, summaries, and notes. Because it is a block-level element, a newline is inserted at the beginning and end of the paragraph. <div align= "" >...</div> is used to set the location of the content block. You can use <div> to bind scripts or styles to any part of a document.
(2) and <div> different,<span> is an inline element that does not cause a newline. It is a logical, inline grouping element. The most common way to use it is to specify a style for several words or even a few characters in a paragraph of text.
(3) You can place the content that needs to be centered in the middle of <center></center>. <center> is the same as <div align = "center" > function.
Examples of the use of:<span> elements.
<p>in this sentence <span class = "Important" >some of the ' text is ' important!</span></p>