1.<!DOCTYPE> declaration:It must appear only once,it represents the document type ,and help the browsers to display web pages correctly.

2.HTML Headings: It consist of 6 headings from <h1> to <h6>tags.

<h1>The most important</h1>

<h6>The least important</h6>

3.HTML paragraphs:It defines that the contents of the tag is paragraph <p> paragraph</p> 4.HTML links: They are  defined by <a> tag. <a href=source link></a> 5.HTML images:They are defined by <img> tag.It has 4 attributes the source file,alternative text,width,and height. <img src="img.jpg" alt="forexample.com" width="100" height="102">

6.Font size: It allows developers to set the size of the written text.

<p style="font-size:30px;">this is a paragraph of font size 30px</p>

<p>this is a paragraph of font size 15px</p>

7.Tables:It allows the users to recognize their information into rows and columns .It is defined by<table> tag .<tr> tag defines row,<th> tag defines header which is bold and centered ,and <td> tag defines a cell which are regular and left-alligned.

<table>
  <tr>
    <th>Firstname</th>
    <th>Lastname</th>
    <th>Age</th>
  </tr>
  <tr>
    <td>Aya</td>
    <td>Hammoud</td>
    <td>20</td>
  </tr>
  <tr>
    <td>Wajdi</td>
    <td>Kayal</td>
    <td>30</td>
  </tr>
</table>

Firstname	Lastname	Age
Aya	Hammoud	20
Wajdi	Kayal	30

8.HTML colors: They are specified by pre-defined names or with RGB, HEX, HSL, RGBA, or HSLA values.

<p style="background-color:Red;">Red</p> 

<p style="background-color:Orange;">Orange</p>

<p style="background-color:Green;">Green</p>

Red

Orange

Green

9.HTML emogis: Emojis look like images, or icons, but they are not.

They are letters (characters) from the UTF-8 (Unicode) character set.

A B C <p> &#65; &#66; &#67;</p> 

<p>&#128512;</p> 😀