THE CSS - THAT IS 'CASCADING STYLE SHEETS' - TO FORMAT WEB PAGES
Lino Bertuzzi - Roma Agosto 2014
(da wikipedia)

CSS (Cascading Style Sheets), in computer science, is a language used to define the formatting of HTML documents, such as XHTML and XML in web sites and related web pages. The rules for composing the CSS are contained in a set of guidelines (Recommendations) issued since 1996 by the W3C.
If you want to know the basics about studying the style sheets on a site created by professionals, you can click this link.
The introduction of CSS was necessary to separate the content from the formatting and programming, to enable a more clear and easy to use codes, both for authors of HTML pages and for users, ensuring at the same time also the reuse of code and one its easier maintainability.
A CSS code can be embedded into the page, or the page may refer to it with a line of instruction that is written among the TAG <head> and </ head> of a web page code.
 
The example statement

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

with this instruction the web page is linked to a file that we called newstyle.css which resides immediately into the DIR named css, or another as you want, which is a subdir of where the website is housed. To use the CSS one must know the English language, to understand the meaning of the word, and choose the appropriated one from the various native words that make up this language.

In my opinion using a specific software such as ADOBE DREAMWEAVER is the best thing, because while you're writing the code the system opens the pull-down menu with the allowed words, and clicking,an instruction to bring it in the code we are writing. Moreover it's possible to check the effect on the page while writing the code itself.

Alternatively we could use to record first your codes on paper tables or on digital media. But using this software allows you to see simultaneously the effect of what you write, while you write it. IF YOU'RE A BEGINNER SHOULD STUDY THESE ITEM FIRST (click here)