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.
CSS selectors are used to "find" (or select) HTML elements based on their element name, id, class, attribute, and more.
This is the same selector we have seen above. Again, one more example to give a color to all level 1 headings:
Rather than selecting elements of a specific type, the universal selector quite simply matches the name of any element type −
This rule renders the content of every element in our document in black.
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.
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.
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:
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:
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.
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 −
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:
In this example all level 2 headings will be displayed in black color when those headings will lie with in tags having id attribute set to black.
You have seen the descendant selectors. There is one more type of selector, which is very similar to descendants but have different functionality. Consider the following example −
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> would not have any effect of this rule.
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 −
You can apply a style to many selectors if you like. Just separate the selectors with a comma, as given in the following example −
Comments are used to explain the code, and may help when you edit the source code at a later date.
Comments are ignored by browsers.
A CSS comment starts with /* and ends with */. Comments can also span multiple lines:
See this example: