!doctype html defines that code written here is html
lang defines the language used in this case its english
meta charset defines which encoding is used here; meta name and content is used to ensure consistancy in view among different browser
title is the title of the page -text written on tab
here stylesheet is linked to this html file via link tag; href specify the location and rel specify the relation ship - stylesheet
inside header there is date time and a text Box-Model.png
Inside body heading is written by h1 tag, the paragraph is written by p tag - both of them uses redborder class
the nested boxes are written using an unordered with parent div redborder and li items with listBorder
footer represent end of the page in footer button tag is used to decorate button and anchor tag a is used to make a link
univeral selector * used to to apply padding (space between element and box), margin (space between border of the box and webpage to 0
padding is the shorthand of padding-left, right, top and bottom - they are used to achieve space between element and border. Padding can be represented in terms of absolute value or percentages.
here i have used 2 types of border listBorder to decorate list element and redBorder for all the rest
border is used to specify the border here the width of border is 3px with sold
height auto is used to automatically adjust height as per content requirements
footer p specify that style should be applied to p which is inside footer tag (nested)
',' between button and a is used to specify that style written should be applicable to both button and anchor a tags
here height and with of button and anchor tag are specified as 60px * 30px
font weight is used to make heading h1 tag larger than usual