Syntax
The CSS syntax is made up of three parts: a selector, a property and a value:| selector {property:value} |
| body {color:black} |
| p {font-family:"sans serif"} |
| p {text-align:center;color:red} |
| p { text-align:center; color:black; font-family:arial } |
Grouping
You can group selectors. Separate each selector with a comma. In the example below we have grouped all the header elements. All header elements will be displayed in green text color:| h1,h2,h3,h4,h5,h6 { color:green } |
The class Selector
With the class selector you can define different styles for the same type of HTML element.Say that you would like to have two types of paragraphs in your document: one right-aligned paragraph, and one center-aligned paragraph. Here is how you can do it with styles:
| p.right {text-align:right} p.center {text-align:center} |
| <p class="right">This paragraph will be right-aligned.</p> <p class="center">This paragraph will be center-aligned.</p> |
| <p class="center bold">This is a paragraph.</p> |
You can also omit the tag name in the selector to define a style that will be used by all HTML elements that have a certain class. In the example below, all HTML elements with class="center" will be center-aligned:
| .center {text-align:center} |
| <h1 class="center">This heading will be center-aligned</h1> <p class="center">This paragraph will also be center-aligned.</p> |
Do NOT start a class name with a number! It will not work in Mozilla/Firefox.Add Styles to Elements with Particular Attributes
You can also apply styles to HTML elements with particular attributes.The style rule below will match all input elements that have a type attribute with a value of "text":
| input[type="text"] {background-color:blue} |
The id Selector
You can also define styles for HTML elements with the id selector. The id selector is defined as a #.The style rule below will match the element that has an id attribute with a value of "green":
| #green {color:green} |
| p#para1 { text-align:center; color:red } |
Do NOT start an ID name with a number! It will not work in Mozilla/Firefox.CSS Comments
Comments are used to explain your code, and may help you when you edit the source code at a later date. A comment will be ignored by browsers. A CSS comment begins with "/*", and ends with "*/", like this:/*This is a comment*/
p
{
text-align:center;
/*This is another comment*/
color:black;
font-family:arial
}How to Insert a Style Sheet
When a browser reads a style sheet, it will format the document according to it. There are three ways of inserting a style sheet:External Style Sheet
An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the look of an entire Web site by changing one file. Each page must link to the style sheet using the <link> tag. The <link> tag goes inside the head section:| <head> <link rel="stylesheet" type="text/css" href="/mystyle.css" /> </head> |
An external style sheet can be written in any text editor. The file should not contain any html tags. Your style sheet should be saved with a .css extension. An example of a style sheet file is shown below:
| hr {color:sienna} p {margin-left:20px} body {background-image:url("images/back40.gif")} |
Do not leave spaces between the property value and the units! "margin-left:20 px" (instead of "margin-left:20px") will only work in IE6, but it will not work in Firefox or Opera.Internal Style Sheet
An internal style sheet should be used when a single document has a unique style. You define internal styles in the head section by using the <style> tag, like this:| <head> <style type="text/css"> hr {color:sienna} p {margin-left:20px} body {background-image:url("images/back40.gif")} </style> </head> |
Note: A browser normally ignores unknown tags. This means that an old browser that does not support styles, will ignore the <style> tag, but the content of the <style> tag will be displayed on the page. It is possible to prevent an old browser from displaying the content by hiding it in the HTML comment element:
| <head> <style type="text/css"> <!-- hr {color:sienna} p {margin-left:20px} body {background-image: url('/images/back40.gif')} --> </style> </head> |
Inline Styles
An inline style loses many of the advantages of style sheets by mixing content with presentation. Use this method sparingly, such as when a style is to be applied to a single occurrence of an element.To use inline styles you use the style attribute in the relevant tag. The style attribute can contain any CSS property. The example shows how to change the color and the left margin of a paragraph:
| <p style="color:sienna;margin-left:20px">This is a paragraph.</p> |
Multiple Style Sheets
If some properties have been set for the same selector in different style sheets, the values will be inherited from the more specific style sheet.For example, an external style sheet has these properties for the h3 selector:
| h3 { color:red; text-align:left; font-size:8pt } |
| h3 { text-align:right; font-size:20pt } |
| color:red; text-align:right; font-size:20pt |
