Css: How to Combine Multiple Stylesheets into One

Concatenate multiple CSS files into one

As long as the ordering of the arguments for cat matches the original ordering of the three referenced CSS files in the HTML file the cat-method should work as expected.

So given say ..

<link href="css/one.css" rel="stylesheet" type="text/css" media="all">
<link href="css/two.css" rel="stylesheet" type="text/css" media="all">
<link href="css/three.css" rel="stylesheet" type="text/css" media="all">

.. the following concaternation ..

cat css/one.css css/two.css css/three.css > css/all.css

.. together will the following reference ..

<link href="css/all.css" rel="stylesheet" type="text/css" media="all">

.. should be 100 % identical.

How to merge and clean 2 css files with overlapping selectors/properties?

There is This and This list of other helpful tools

css best practices - combining all css into a single stylesheet?

You should combine all your CSS into one file to reduce the amount of requests made to your server.

A similar topic is sprite sheets, the combination of multiple images into one large image to also reduce the amount of requests made to your server.

You'll find that loading 100x 5kb files is a lot slower than loading a single 500kb file.

When you're ready to upload your files to a live environment, you should also consider compressing your CSS and JavaScript files. There are a vast amount of online tools for this, eg:

CSS Compressor.
JavaScript Compressor.
HTML Compressor.

Combine css external links to one link

Use CSS Import Rules

<link rel="stylesheet" type="text/css" href="/css/Combined.css" />

Combined Css Inside you can import all other css like below

@import url('/css/s1.css');
@import url('/css/s2.css');
@import url('/css/s3.css');

for more information read below article

http://www.cssnewbie.com/css-import-rule/#.U2CN9Pk70dE

combine multiple css styles into one

In bootstrap 4, the css for .alert is

.alert {
    position: relative;
    padding: 0.75rem 1.25rem;
    margin-bottom: 1rem;
    border: 1px solid transparent;
    border-radius: 0.25rem;
}

and for .alert-secondary

.alert-secondary {
    color: #464a4e;
    background-color: #e7e8ea;
    border-color: #dddfe2;
}

So to combine them, use:

.login-alert-combined{
    font-family: 'Kavivanar', cursive;
    position: relative;
    padding: 0.75rem 1.25rem;
    margin-bottom: 1rem;
    border: 1px solid transparent;
    border-radius: 0.25rem;
    color: #464a4e;
    background-color: #e7e8ea;
    border-color: #dddfe2;
}

But I don't see what is wrong with setting class as "alert alert-secondary login-alert" when you want to use all 3 styles.