CSS Syntax

CSS Syntax

A CSS rule consists of a set of style rules that are interpreted by the browser and then applied to the corresponding elements in the document.

Syntax

CSS rules have two main parts, a selector and one or more declarations:

CSS Selector Syntax Illustration

Selectors are used to declare which of the markup elements a style applies to.

The declarations that appear in the block that follows the selector may be applied to all elements of a specific type, or only those elements that match a certain attribute. You will learn more about selectors in next chapter.

Each declaration consists of a property and a value. The property is the style attribute you want to change; they could be color or border etc. Each property has a value, for example color property can have value either blue or #0000FF etc.

h1 {color:blue; text-align:center;}

To make the CSS more readable, you can put one declaration on each line, like this:

Example :

h1 {
    color: blue;
    text-align: center;
}

In the example above h1 is a selector, color and text-align are properties and given blue and center are the corresponding values of these properties.

CSS Comments :

Comments are usually added with the purpose of making the source code easier to understand. It may help other developer (or you in the future when you edit the source code) to understand what you were trying to do with the CSS. Comments are significant to programmers but typically ignored by browsers.

A CSS comment begins with /*, and ends with */, See the example below:

Example :

/* This is a CSS comment */
h1 {
    color: blue;
    text-align: center;
}

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 a 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, border etc.

Value − Values are assigned to properties. For example, color property can have value either red or #F1F1F1 etc.

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;
}

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 line or multiple lines. For better readability, we keep them in separate lines.

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 like. 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 applicable to h1, h2 and h3 element as well. The order of the list is irrelevant. All the elements in the selector will have the corresponding declarations applied to them.