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HTML

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About the <head>

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

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Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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HTML 

              
                .centerline

h1 Problem
h2 float 1
.row.float-1
    .left left
    .center center
    .right right
br
.row.float-1
    .left left
    .center center
    .right rightreallylongtexthere

h2 flex 1
.row.flex-1
    .left left
    .center center
    .right right
br
.row.flex-1
    .left left
    .center center
    .right rightreallylongtexthere

br
br
br

h1 Solution
h2 float 2 
.row.float-2
    span.left
        span left
    span.center 
        span center
    span.right 
        span right
br
.row.float-2
    span.left
        span left
    span.center 
        span center
    span.right 
        span rightreallylongtexthere

h2 flex 2
.row.flex-2
    span.left
        span left
    span.center 
        span center
    span.right 
        span right
br
.row.flex-2
    span
        .left left
    span
        .center center
    span
        .right rightreallylongtexthere
br
br
!

CSS 

              
                @mixin flexbox($d, $w, $j, $a){
    display: flex;
    flex-direction: $d;
    flex-wrap: $w;
    justify-content: $j;
    align-items: $a;
}

@mixin clearfix() {
    &:after {
        content: "";
        display: table;
        clear: both;
    }
}

.centerline{
    position: fixed;
    top: 0;
    left: 50%;
    width: 10px;
    height: 100%;
    background: red;
    transform: translateX(-50%);
    opacity: .5;
}

.row{
    position: relative;
    margin: 0 auto;
    width: 80%;
    max-width: 1400px;
    font-family: Roboto, Calibri, Arial;
    font-size: 20px;
    border: 1px solid black;
    background: rgba(black, .2);
    
    .left, .right, .center{
        background: rgba(white, .8);
    }
}

.float-1{
    @include clearfix();
    text-align: center;
        
    .left{
        float: left;
    }
    
    .right{
        float: right;
    }    
    
    .center{
        margin: 0 auto;
        display: inline-block;
        position: relative;
    }
}


.float-2{
    @include clearfix();
    text-align: center;
    
    span{
        width: (100%/3);
        &:nth-of-type(1){
            text-align: left;
        }
        &:nth-of-type(2){
            text-align: center;
        }
        &:nth-of-type(3){
            text-align: right;
        }
    }
    
    .left{
        float: left;
    }
    
    .right{
        float: right;
    }    
}

.flex-1{
    @include flexbox(row, wrap, space-between, center);
}

.flex-2{
    @include flexbox(row, wrap, flex-start, center);
    span{
        flex: 1;
        &:nth-of-type(1){
            text-align: left;
        }
        &:nth-of-type(2){
            text-align: center;
        }
        &:nth-of-type(3){
            text-align: right;
        }
    }
}

h1,
h2 {
    padding: 0 10%;
}
!

JS
!
999px

Console