Use the concept of oocss , which is nothing more than to create modularized css snippets, for example: link
.button {
display: inline-block;
padding: 10px 20px;
background-color: #ccc;
color: #333;
text-decoration: none;
white-space: nowrap;
border-radius: 5px;
}
.button:focus,
.button:active,
.button:hover {
outline: 0;
color: #fff;
}
.button-danger {
background-color: #e74c3c;
color: #fff;
}
.button-danger:hover {
background-color: #c0392b;
}
Here is a very simple example, but it demonstrates a component that you can include in several pages as many times as you want. and if you need to create a custom button, just create a new class that overrides the appearance of this button, but without harming others, obviously when using this approach, you never override the main classes if you do not commit all your work .
I have read some excellent books on this subject, and about css class nomenclatures that facilitate this modularized css approach:
BEM - Article , another article .
SMACSS - ITCSS - Slide .