Changing web page content
In your HTML5 code, you no doubt will have lots of text that appears in separate sections of your web page. For example, you may have a sidebar element that lists the day’s news events related to your website topic, or you may have a header element that displays the current time and temperature for your city.
Changing web page styles
You add CSS3 styles to your web pages to apply styles to text and elements, or to place elements in specific locations on the web page. The CSS3 code you create is placed inline in the HTML5 elements, internally in the head element of the web page, or as an external style sheet.
display style property, which you use to determine how or if the element appears on the web page.
display style property for any element on the web page to make it appear as needed or disappear when not needed. That gives you the ability to dramatically alter the layout of a web page at any time while your site visitor is interacting with the web page. This helps hide sections that may be distracting to site visitors at times, then make them appear when the site visitor needs to interact with them.