CSS Tutorial Part 1

CSS is used to control the style of a web document in a simple and easy way.
CSS stands for Cascading Style Sheet.
This tutorial gives complete understanding on CSS. 

CSS Introduction 

Before your begin: 

Before you begin, it's important that you know Windows or Unix. A working knowledge of Windows or Unix makes it much easier to learn HTML. 

You should be familiar with: 

•  Basic word processing using any text editor. 
•  How to create directories and files. 
•  How to navigate through different directories. 
•  Basic understanding on internet browsing using a browser like Internet Explorer or Firefox etc. 
•  Basic understanding on developing simple Web Pages using HTML or XHTML.

What is CSS? 

Cascading Style Sheets, fondly referred to as CSS, is a simple design language intended to simplify the process of making web pages presentable. 

CSS handles the look and feel part of a web page. Using CSS, you can control the color of the text, the style of fonts, the spacing between paragraphs, how columns are sized and laid out, what background images or colors are used, as well as a variety of other effects. 

CSS is easy to learn and understand but it provides powerful control over the presentation of an HTML document. Most commonly, CSS is combined with the markup languages HTML or XHTML.

Advantages of CSS: 

•  CSS saves time - You can write CSS once and then reuse same sheet in multiple HTML pages. You can define a style for each HTML element and apply it to as many Web pages as you want.
• Pages load faster - If you are using CSS, you do not need to write HTML tag attributes every time. Just write one CSS rule of a tag and apply to all the occurrences of that tag. So less code means faster download times. 
•  Easy maintenance - To make a global change, simply change the style, and all elements in all the web pages will be updated automatically. 
•  Superior styles to HTML - CSS has a much wider array of attributes than HTML so you can give far better look to your HTML page in comparison of HTML attributes. 
•  Multiple Device Compatibility - Style sheets allow content to be optimized for more than one type of device. By using the same HTML document, different versions of a website can be presented for handheld devices such as PDAs and cell phones or for printing. 
•  Global web standards - Now HTML attributes are being deprecated and it is being recommended to use CSS. So its a good idea to start using CSS in all the HTML pages to make them compatible to future browsers.

Who Creates and Maintains CSS? 

CSS is created and maintained through a group of people within the W3C called the CSS Working Group. The CSS Working Group creates documents called specifications. When a specification has been discussed and officially ratified by W3C members, it becomes a recommendation. 

These ratified specifications are called recommendations because the W3C has no control over the actual implementation of the language. Independent companies and organizations create that software. 

NOTE: The World Wide Web Consortium, or W3C is a group that makes recommendations about how the Internet works and how it should evolve.

CSS Syntax – Selectors

A CSS comprises of style rules that are interpreted by the browser and then applied to the corresponding elements in your document. A style rule is made of three parts: 

•  Selector: A selector is an HTML tag at which style will be applied. This could be any tag like <h1> or <table> etc. 
•  Property: A property is a type of attribute of HTML tag. Put simply, all the HTML attributes are converted into CSS properties. They could be color or border etc. 
•  Value: Values are assigned to properties. For example color property can have value either red or #F1F1F1 etc. 

You can put CSS Style Rule Syntax as follows: 

selector { property: value } 

Example: You can define a table border as follows:

table{ color: red; }

Here table is a selector and color is a property and given value red is the value of that property. 

You can define selectors in various simple ways based on your comfort. Let me put these selectors one by one.

1. The Type Selectors
2. The Universal Selectors
3. The Descendant Selectors
4. The Class Selectors
5. The ID Selectors
6. The Child Selectors
7. The Attribute Selectors

The Type Selectors: 

This is the same selector we have seen above. Again one more example to give a color to all level 1 headings : 

h1 {     color: #36CFFF;  } 

The Universal Selectors: 

Rather than selecting elements of a specific type, the universal selector quite simply matches the name of any element type : 

* {    color: #000000;  } 

This rule renders the content of every element in our document in black. 

The Descendant Selectors: 

Suppose you want to apply a style rule to a particular element only when it lies inside a particular element. As given in the following example, style rule will apply to <em> element only when it lies inside <ul> tag. 

ul em {   color: #000000;  } 

The Class Selectors: 

You can define style rules based on the class attribute of the elements. All the elements having that class will be formatted according to the defined rule. 

.black {   color: #000000;  } 

This rule renders the content in black for every element with class attribute set to black in our document. You can make it a bit more particular. For example: 

h1.black {   color: #000000;  }

This rule renders the content in black for only <h1> elements with class attribute set to black. 

You can apply more than one class selectors to given element. Consider the following example : 

<p class="center bold"> This para will be styled by the classes center and bold. </p> 

The ID Selectors: 

You can define style rules based on the id attribute of the elements. All the elements having that id will be formatted according to the defined rule. 

#black {   color: #000000;  } 

This rule renders the content in black for every element with id attribute set to black in our document. You can make it a bit more particular. For example: 

h1#black {   color: #000000;  } 

This rule renders the content in black for only <h1> elements with id attribute set to black.  

The true power of id selectors is when they are used as the foundation for descendant selectors, For 

example: 

#black h2 {   color: #000000;  } 

In this example all level 2 headings will be displayed in black color only when those headings will lie with in tags having id attribute set to black. 

The Child Selectors: 

You have seen descendant selectors. There is one more type of selectors which is very similar to descendants but have different functionality. Consider the following example: 

body > p {   color: #000000;  } 

This rule will render all the paragraphs in black if they are direct child of <body> element. Other paragraphs put inside other elements like <div> or <td> etc. would not have any effect of this rule. 

The Attribute Selectors: 

You can also apply styles to HTML elements with particular attributes. The style rule below will match all input elements that has a type attribute with a value of text: 

 

input[type="text"]{   color: #000000;  } 

The advantage to this method is that the <input type="submit" /> element is unaffected, and the color applied only to the desired text fields. 

There are following rules applied to attribute selector. 

•  p[lang] - Selects all paragraph elements with a lang attribute. 
•  p[lang="fr"] - Selects all paragraph elements whose lang attribute has a value of exactly "fr". 
•  p[lang~="fr"] - Selects all paragraph elements whose lang attribute contains the word "fr". 
•  p[lang|="en"] - Selects all paragraph elements whose lang attribute contains values that are exactly "en", or begin with "en-".