Classes and IDs | HTML: Classes and IDs both are using to access the particular element in CSS or in JS. Here is the ClassesAndIds.html: <!DOCTYPE html> <html lang="en" dir="ltr"> <head> <style> .class { font-size: 20px; background-color: yellow; } #id001 { font-size: 30px; background-color: orange; } #id007 { font-size: 40px; background-color: lightblue; } </style> <title>Classes and Ids</title> </head> <body> <!-- Classes --> <div class="class"> <h3>Class</h3> <p>bla bla bla</p> </div> <span class="class">bla bla bla</span> <!-- Ids --> <div id="id001"> <h3>Id</h3> <p>bla bla bla</p> </div> <span id="id007">bla bla b