To add a red border to an element, you need to implement the border-danger class.Red border implement danger and you can set danger messages inside it.Implementing the border-danger is quite easy −   Red Border Let us see an example to work with the border-danger Bootstrap 4 class −ExampleLive Demo       Bootstrap Example                             .new {       width: 120px;       height: 120px;       margin: 20px;     }             Rectangle with red border:     Red Border  

To add top rounded corners to an element, use the rounded-top class in Bootstrap 4.I have taken div as the element −Let us learn how to add top rounded corners to an element −ExampleLive Demo       Bootstrap Example                             .new {       width: 80px;       height: 80px;       background-color: #EE6D1E;       margin: 20px;     }             Rounded Corner     We have a rectangle with top rounded corner:      

To align flex items on small, medium, large and extra large screen size, use the justify-content-*-start class.Let us see first for small screen size −   Interface   Packages   Multithreading In the same way, implement it for medium, large and extra large screen size like the following −justify-content-md-start: Medium Screen size justify-content-lg-start: Large Screen size justify-content-xl-start: Extra Large Screen SizeYou can try to run the following code to align flex items in the start on different screen sizes −ExampleLive Score       Bootstrap Example                             Java Topics           Interface       Packages       Multithreading               Interface       Packages       Multithreading               Interface       Packages       Multithreading      

Use the justify-content-start class in Bootstrap to justify content in the beginning.The justify-content-*-start class is used in Bootstrap to justify content in the beginning on different screen sizes like the following on small, medium, and large screen sizes −You can try to run the following code to implement the justify-content-*-start class −ExampleLive Demo       Bootstrap Example                                 Entertainment           Bollywood       Tollywood       Hollywood               Bollywood       Tollywood       Hollywood                Bollywood        Tollywood        Hollywood      

Use the card-header-tabs in Bootstrap to style navigation links in card header −             Drupal Commerce               WooCommerce       The header tabs are set on Unordered List using nav-tabs and card-header-tabs class as shown above −Let us see an example to learn how to create Bootstrap 4 card header − ExampleLive Demo       Bootstrap Example                               E-commerce Technologies                                         Drupal Commerce                                 WooCommerce                                 Prestashop                                 Shopify                                 Add title here       Add content here          

Use the rounded-top class in Bootstarp 4 to set top rounded corners to an element.Using the class, I have set two rectangles using the same class − A new class is also set for div, to style it, .new {   width: 60px;   height: 60px;   background-color: #26CF12;   margin: 20px; } You can try to run the following code to implement the rounded-top class −ExampleLive Demo      Bootstrap Example                            .new {      width: 60px;      height: 60px;      background-color: #26CF12;      margin: 20px;    }           Rounded Corner     We have two rectangles with top rounded corner:          

To create an inline flexbox container, use the d-inline-flex class in Bootstrap.Use the d-*-inline-flex class in Bootstrap to set the same inline flexbox container on specific screen size −Small Screen Size   Small Medium Screen Size   Medium Large Screen Size   Large Let us see an example to learn how to create inline flexbox container on a specific screen size −ExampleLive Demo       Bootstrap Example                             Working with Inline Flex     Resize the browser window to check the effect     d-flex       d-sm-flex       d-md-flex       d-lg-flex       d-xl-flex    

To add left rounded corners to an element like , then use the rounded-left class in Bootstarp 4.To set rounded left corners −You can try to run the following code to implement rounded-left class −ExampleLive Demo       Bootstrap Example                             .one {       width: 200px;       height: 100px;       background-color: #FFFF00;       margin: 8px;     }             Rounded Corner     We have three rectangles with left rounded corner:              

Use the .justify-content-*-end class to align flex items in the end on different screen sizes like this −For small screen size, use −justify-content-sm-endFor medium screen size, use −justify-content-md-endFor large screen size, use −justify-content-lg-endLet us see how to align flex items horizontally on small, medium and large screen sizes −ExampleLive Demo       Bootstrap Example                             Form of Tea           Black Tea       Green Tea       Indian Tea               Black Tea       Green Tea       Indian Tea               Black Tea       Green Tea       Indian Tea      

Use the justify-content-*-center class in Bootstrap 4 to center content on different screen sizes.For different screen sizes −justify-content-sm-center: Small Screen Size justify-content-md-center: Medium Screen Size justify-content-lg-center: Large Screen Size justify-content-xl-center: Extra Large Screen SizeLet us see how to implement the justify-content-*-center class −ExampleLive Demo       Bootstrap Example                             Vehicle           Car       Bike       Truck               Car       Bike       Truck               Car       Bike       Truck               Car       Bike       Truck