CSS (Cascading Style Sheets) is a style sheet language used to describe the presentation of HTML documents, including colors, fonts, layout, etc. CSS saves time by allowing consistent styling across pages and devices. CSS works by defining rules that assign properties and values to HTML elements using selectors. Styles can be defined internally, externally, or inline. When multiple styles conflict, the last read style takes precedence.

1. CSSCascading Style Sheets

2. What is CSS?
O CSS stands for Cascading Style Sheets
O CSS describes how HTML elements are to be
displayed on screen or on a web page.
O CSS is a style language that defines layout of HTML
documents. For example, CSS covers fonts, colours,
margins, lines, height, width, background images and
many other things.
O CSS files can help define font, size, colour, spacing,
border and location of HTML information on a web
page, and can also be used to create a continuous look
throughout multiple pages of a website.
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3. Why css?
O Saves Your Time
O Saves Your Visitors Time(less loading time)
O Gives You Design Flexibility
O Easier to maintain and update
O Multiple Device Compatibility
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4. How it works?
O Syntax:
property : value;
O Ex:
color: red;
What is important to remember is that both
properties and values are case-sensitive in
CSS. The property and value in each pair is
separated by a colon (:).
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5. O CSS declaration blocks:
• The declaration block contains one or more
declarations separated by semicolons.
• Each declaration includes a CSS property name and a
value, separated by a colon.
• A CSS declaration always ends with a semicolon, and
declaration blocks are surrounded by curly braces.
O Syntax:
Selector{property : value;
property : value;
}
The selector points to the HTML element you want to style.
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6. OEx : p {
color: red;
text-align: center;
}
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7. CSS Selectors
O CSS selectors are used to "find" (or select) HTML
elements based on their element name, id, class
and attribute.
O The element Selector
• The element selector selects elements based on
the element name.
Ex:
You can select all <p> elements on a page like the
example on next slide..
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9. O The id Selector
• The id selector uses the id attribute of an HTML
element to select a specific element.
• The id of an element should be unique within a
page, so the id selector is used to select one
unique element!
• To select an element with a specific id, write a hash
(#) character, followed by the id of the element.
• The style rule in example (next slide) will be applied
to the HTML element with id="para1“ and also
different with id=“para2”.
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10. Note: An id name cannot start with a number! By Hansa(Hansika)
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11. O The class selector selects elements with a specific
class attribute.
O To select elements with a specific class, write a period
(.) character, followed by the name of the class.(P
sector in example)
O You can also specify that only specific HTML elements
should be affected by a class.(h1 sector in example)
O You will see both method’s example on next slide..
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12. Note: A class name cannot start with a number! By Hansa(Hansika)
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13. O Grouping Selectors
• If you have elements with the same style definitions.
• It will be better to group the selectors, to minimize the
code.
• To group selectors, separate each selector with a
comma.
Instead of write like this, you can write in
this sorter way
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15. O CSS Comments
• 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:
O Ex:
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16. How to insert CSS?
O There are three ways of inserting a style sheet:
• External style sheet
• Internal style sheet
• Inline style
1. External Style Sheet:
• With an external style sheet, you just need to create
separate css file where you manage entire look of your
website.
• Each page must include a reference to the external style
sheet file inside the <link> element. The <link> element
goes inside the <head> section. By Hansa(Hansika)
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17. O An external style sheet can be written in any text editor.
The file should not contain any html tags. The style
sheet file must be saved with a .css extension.
O Ex: This is how test.css file look
like
Output
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18. 2. Internal Style Sheet:
• An internal style sheet may be used if one single
page has a unique style.
• Internal styles are defined within the <style>
element, inside the <head> section of an HTML
page.
• The downside of using an internal stylesheet is that
changes to the internal stylesheet only effect the
page the code is inserted into.
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20. 3. Inline Styles:
• An inline style may be used to apply a unique style for
a single element.
• To use inline styles, add the style attribute to the
relevant element. The style attribute can contain any
CSS property.
• Ex:
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21. Multiple Style Sheets
O If some properties have been defined for the same
selector (element) in different style sheets, the value
from the last read style sheet will be used.
O Ex:
• Assume that an external style sheet (mystyle.css)has the
following style for the <h1> element:
mystyle.css
h1{
color: navy;
}
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23. Few examples:
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