HTML(Alt)

Question

while importing a image in html it is necessary to write all nd Why ?

<img src="tree.jpg" height="150px" width="150px" alt="" />

Answer 1

Understand this, that <Img src=".Jpg " is important because it gives the input to computer for which image you want to show. And if we talk about full syntax then yes it is important because this show will give an input to computer for the size (length and width ) of the image.thats why full syntax is important.

Answer 2

Alt value defines alternative text to be displayed if the browser not able to show image or image is not supported to display there....
You can mention only what ever you need, if you don't add, then default values are used by brouser.
Edit:
https://www.w3schools.com/tags/att_img_alt.asp