Topic #1- HTML has several semantic elements that define the different parts of a web page:

header - Defines a header for a document or a section

nav - Defines a set of navigation links

section - Defines a section in a document

article - Defines an independent, self-contained content

aside - Defines content aside from the content (like a sidebar)

footer - Defines a footer for a document or a section

details - Defines additional details that the user can open and close on demand

summary - Defines a heading for the details element

Topic #2-There are four different techniques to create multicolumn layouts. Each technique has its pros and cons:

If you want to create your layout fast, you can use a CSS framework,It is common to do entire web layouts using the CSS float property.

Float is easy to learn - you just need to remember how the float and clear properties work.

Disadvantages: Floating elements are tied to the document flow, which may harm the flexibility.

The CSS Grid Layout Module offers a grid-based layout system, with rows and columns, making it easier to design web pages without having to use floats and positioning.

Topic #3: In HTML there are some semantic elements that can be used to define different parts of a web page:

The section element defines a section in a document.

According to W3C's HTML documentation: "A section is a thematic grouping of content, typically with a heading."The article element specifies independent, self-contained content.

An article should make sense on its own, and it should be possible to distribute it independently from the rest of the web site.

"The header element represents a container for introductory content or a set of navigational links.A header element typically contains:one or more heading elements, logo or icon, and authorship information.

According to the W3C: "A semantic Web allows data to be shared and reused across applications, enterprises, and communities."