Question

Sorry, but no matter how often I read it, I just don’t grok it.

I have declared

.submit_button  
{  
  font: 12px Arial;  
  margin:0px;  
  padding:2px;  
}

and now I want to declare centered_submit_button which inherits from submit_button and adds margin-left:auto; margin-right:auto;

Please take pity on me …

Answer 1

Unfortunately, vanilla CSS doesn’t have any notion of inheritance, but you can achieve what you need with this:

.submit_button, .centered_submit_button
{
    font: 12px Arial;  
    margin: 0px;  
    padding: 2px; 
}

.centered_submit_button
{
    margin-left: auto;
    margin-right: auto;
}

This is probably all that you need, but as scurker mentioned, there are CSS-enhancing tools such as LESS that provide inheritance-like constructs as well as many other nice features that can improve your quality-of-life as a web developer.

In this case, LESS is ironically more verbose, but arguably more expressive:

.button ()
{
    font: 12px Arial;
    margin: 0px;  
    padding: 2px; 
}

.submit_button
{
    .button;
}

.centered_submit_button
{
    .button;
    margin-left: auto;
    margin-right: auto;
}

Another similar tool is Stylus, which does most of what LESS does, but also has a very indifferent attitude about using punctuation in your syntax:

button()
    font 12px Arial
    margin 0px
    padding 2px

.submit_button
    button

.centered_submit_button
    button
    margin-left auto
    margin-right auto

Both LESS and Stylus have client-side JavaScript implementations, so you have the option to host your .less or .stylus files directly or to compile them on the server and host the resulting CSS.