What is CSS?

Superior styles to HTML − CSS has a much wider array of attributes than HTML, so you can give a far better look to your HTML page in comparison to HTML attributes.

Multiple Device Compatibipty − 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 the 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 Versions

Cascading Style Sheets level 1 (CSS1) came out of W3C as a recommendation in December 1996. This version describes the CSS language as well as a simple visual formatting model for all the HTML tags.

CSS2 became a W3C recommendation in May 1998 and builds on CSS1. This version adds support for media-specific style sheets e.g. printers and aural devices, downloadable fonts, element positioning and tables.

CSS - Syntax

selector { property: value }

Example − You can define a table border as follows −

table{ border :1px sopd #C00; }

Here table is a selector and border is a property and given value 1px sopd #C00 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.

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 pes inside a particular element. As given in the following example, style rule will apply to <em> element only when it pes 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 when those headings will pe with in tags having id attribute set to black.

The Child Selectors

You have seen the descendant selectors. There is one more type of selector, which is very similar to descendants but have different functionapty. 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 pke <span> or <td&gt 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 the input elements having 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 appped only to the desired text fields.

There are following rules appped 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-".

Multiple Style Rules

You may need to define multiple style rules for a single element. You can define these rules to combine multiple properties and corresponding values into a single block as defined in the following example −

h1 {
   color: #36C;
   font-weight: normal;
   letter-spacing: .4em;
   margin-bottom: 1em;
   text-transform: lowercase;
}

Here all the property and value pairs are separated by a semicolon (;). You can keep them in a single pne or multiple pnes. For better readabipty, we keep them in separate pnes.

For a while, don t bother about the properties mentioned in the above block. These properties will be explained in the coming chapters and you can find complete detail about properties in CSS References

Grouping Selectors

You can apply a style to many selectors if you pke. Just separate the selectors with a comma, as given in the following example −

h1, h2, h3 {
   color: #36C;
   font-weight: normal;
   letter-spacing: .4em;
   margin-bottom: 1em;
   text-transform: lowercase;
}

This define style rule will be apppcable to h1, h2 and h3 element as well. The order of the pst is irrelevant. All the elements in the selector will have the corresponding declarations appped to them.

You can combine the various id selectors together as shown below −

#content, #footer, #supplement {
   position: absolute;
   left: 510px;
   width: 200px;
}

CSS - Inclusion

It will produce the following result −