Bootstrap

Adding bootstrap-----------------
 bootstrap is a CSS framework with inbuilt classes. resizing of elements is adone automatically in bootstrap
 
To add bootstap add the following link to your file:-
   <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"/>

To add a comment---
<!-- abc -->

Libraries in Bootstrap---------------
  <div class="container-fluid">                             utilizes 100% of the viewport
  <img class="img-responsive">                              fits the image to 100% of the screen
  <h2 class= "text-center">                                 text-center - shifts text to center (can be used with other text tags)
                                                            text-primary - gives blue color to the text
  
  BUTTON------
  <button class="btn btn-default">(basic button)            btn - grey colour button with smooth edges and spacing
                                                            btn-default - colour animation to the button 
  (btn btn-default is recommended to be added with every button)                                                          
  <button class="btn-block">                                creates a button covering 100% width of screen        
  <button class="btn-primary">                              creates a classic button with blue colour
  <button class="btn-info">                                 creates a classic button with light blue colour
  <button class="btn-danger">                               creates a classic button with red colour
  
  GRID--------
  (div is used)
  <div class="row">                                         creates a row
  <div class="col-xs-4">                                    col     - creates a column
                                                            xs/md   - size of button (xs-extra small, md-medium)
                                                            1/2/3.. - width of button
  inline editing
  <span class="text-danger">                                used for inline editing (this tag changes the color to red) 
  
  TO TARGET INLINE ELEMENTS--------
  <span class="text-danger">abc</span>                      to bring changes to an inline text
  
  Adding FONT AWESOME----------
  <i class="fas fas-thumbs-up">...</i>                     i is used to add font awesome to a particular part 
                                                           fas              - to add font awesome
                                                           fa-thumbs-up     - to add thumbs up icon
                                                           fa-info-circle   - to add info circle sign
                                                           fa-trash         - to add trashbin sign
                                                           fa-paper-plane   - to add a paperplane sign
                                                           
   Adding DEPTH to elements-----------
   <div class="well">..</div>                              it is used to give a visual depth to an element