CSS stands for Cascading Style Sheet. CSS are basically three types

1.Inline CSS

2.Internal CSS (Means HTMl+CSS code write in a single page and it is save by .html extension)

3.External CSS

Every CSS Program we can Save by .CSS extension(if you call Externally i.e external css)

In CSS we can used id and class using # sign we can represent id and using . sign we can represent class.

class and id both are alphabetic . alphanumeric but numeric is not allowed and first character must be Alphabet.

for ex:

#abc , #ab12 are allowed.

#123, #1ab are not allowed.

same with class

.abc , .ab45 are allowed.

.123 , .1adc are not allowed.

Note: - We can't called two id / two class in a single tag if you called than only one is working so whose working those called first

Applications of CSS

1. You can write CSS once and then reuse same sheet in multiple HTML pages. You can define a style for each HTML element and apply it to as many Web pages as you want.

2.If you are using CSS, you do not need to write HTML tag attributes every time. Just write one CSS rule of a tag and apply it to all the occurrences of that tag. So less code means faster download times.

3.To make a global change, simply change the style, and all elements in all the web pages will be updated automatically.