Saturday, 11 February 2012

Monday, 2 January 2012

HTML Colors

Color Values

HTML colors are defined using a hexadecimal notation (HEX) for the combination of Red, Green, and Blue color values (RGB).
The lowest value that can be given to one of the light sources is 0 (in HEX: 00). The highest value is 255 (in HEX: FF).
HEX values are specified as 3 pairs of two-digit numbers, starting with a # sign.

Color Values

Color Color HEX Color RGB
#000000 rgb(0,0,0)
#FF0000 rgb(255,0,0)
#00FF00 rgb(0,255,0)
#0000FF rgb(0,0,255)
#FFFF00 rgb(255,255,0)
#00FFFF rgb(0,255,255)
#FF00FF rgb(255,0,255)
#C0C0C0 rgb(192,192,192)
#FFFFFF rgb(255,255,255)

Try it yourself »

16 Million Different Colors


Web Safe Colors?

Some years ago, when computers supported max 256 different colors, a list of 216 "Web Safe Colors" was suggested as a Web standard, reserving 40 fixed system colors.
The 216 cross-browser color palette was created to ensure that all computers would display the colors correctly when running a 256 color palette.
This is not important today, since most computers can display millions of different colors. Anyway, here is the list:
000000 000033 000066 000099 0000CC 0000FF
003300 003333 003366 003399 0033CC 0033FF
006600 006633 006666 006699 0066CC 0066FF
009900 009933 009966 009999 0099CC 0099FF
00CC00 00CC33 00CC66 00CC99 00CCCC 00CCFF
00FF00 00FF33 00FF66 00FF99 00FFCC 00FFFF
330000 330033 330066 330099 3300CC 3300FF
333300 333333 333366 333399 3333CC 3333FF
336600 336633 336666 336699 3366CC 3366FF
339900 339933 339966 339999 3399CC 3399FF
33CC00 33CC33 33CC66 33CC99 33CCCC 33CCFF
33FF00 33FF33 33FF66 33FF99 33FFCC 33FFFF
660000 660033 660066 660099 6600CC 6600FF
663300 663333 663366 663399 6633CC 6633FF
666600 666633 666666 666699 6666CC 6666FF
669900 669933 669966 669999 6699CC 6699FF
66CC00 66CC33 66CC66 66CC99 66CCCC 66CCFF
66FF00 66FF33 66FF66 66FF99 66FFCC 66FFFF
990000 990033 990066 990099 9900CC 9900FF
993300 993333 993366 993399 9933CC 9933FF
996600 996633 996666 996699 9966CC 9966FF
999900 999933 999966 999999 9999CC 9999FF
99CC00 99CC33 99CC66 99CC99 99CCCC 99CCFF
99FF00 99FF33 99FF66 99FF99 99FFCC 99FFFF
CC0000 CC0033 CC0066 CC0099 CC00CC CC00FF
CC3300 CC3333 CC3366 CC3399 CC33CC CC33FF
CC6600 CC6633 CC6666 CC6699 CC66CC CC66FF
CC9900 CC9933 CC9966 CC9999 CC99CC CC99FF
CCCC00 CCCC33 CCCC66 CCCC99 CCCCCC CCCCFF
CCFF00 CCFF33 CCFF66 CCFF99 CCFFCC CCFFFF
FF0000 FF0033 FF0066 FF0099 FF00CC FF00FF
FF3300 FF3333 FF3366 FF3399 FF33CC FF33FF
FF6600 FF6633 FF6666 FF6699 FF66CC FF66FF
FF9900 FF9933 FF9966 FF9999 FF99CC FF99FF
FFCC00 FFCC33 FFCC66 FFCC99 FFCCCC FFCCFF
FFFF00 FFFF33 FFFF66 FFFF99 FFFFCC FFFFFF

HTML Iframes

An iframe is used to display a web page within a web page.
Syntax for adding an iframe:
<iframe src="URL"></iframe>
The URL points to the location of the separate page.

Iframe - Set Height and Width

The height and width attributes are used to specify the height and width of the iframe.
The attribute values are specified in pixels by default, but they can also be in percent (like "80%").

Example

<iframe src="demo_iframe.htm" width="200" height="200"></iframe>

Try it yourself »


Iframe - Remove the Border

The frameborder attribute specifies whether or not to display a border around the iframe.
Set the attribute value to "0" to remove the border:

Example

<iframe src="demo_iframe.htm" frameborder="0"></iframe>

Try it yourself »


Use iframe as a Target for a Link

An iframe can be used as the target frame for a link.
The target attribute of a link must refer to the name attribute of the iframe:

Example

<iframe src="demo_iframe.htm" name="iframe_a"></iframe>
<p><a href="http://www.w3schools.com" target="iframe_a">W3Schools.com</a></p>

Try it yourself »


HTML iframe Tag

Tag Description
<iframe> Defines an inline sub window (frame)

HTML Frames

With frames, several Web pages can be displayed in the same browser window.
ATTENTION. Do not expect frames to be supported in future versions of HTML.

HTML Frames

With frames, you can display more than one HTML document in the same browser window. Each HTML document is called a frame, and each frame is independent of the others.
The disadvantages of using frames are:
  • Frames are not expected to be supported in future versions of HTML
  • Frames are difficult to use. (Printing the entire page is difficult).
  • The web developer must keep track of more HTML documents

The HTML frameset Element

The frameset element holds one or more frame elements. Each frame element can hold a separate document.
The frameset element states HOW MANY columns or rows there will be in the frameset, and HOW MUCH percentage/pixels of space will occupy each of them.

The HTML frame Element

The <frame> tag defines one particular window (frame) within a frameset.
In the example below we have a frameset with two columns.
The first column is set to 25% of the width of the browser window. The second column is set to 75% of the width of the browser window. The document "frame_a.htm" is put into the first column, and the document "frame_b.htm" is put into the second column:
<frameset cols="25%,75%">
   <frame src="frame_a.htm" />
   <frame src="frame_b.htm" />
</frameset>
Note: The frameset column size can also be set in pixels (cols="200,500"), and one of the columns can be set to use the remaining space, with an asterisk (cols="25%,*").


Basic Notes - Useful Tips

Tip: If a frame has visible borders, the user can resize it by dragging the border. To prevent a user from doing this, you can add noresize="noresize" to the <frame> tag.
Note: Add the <noframes> tag for browsers that do not support frames.
Important: You cannot use the <body></body> tags together with the <frameset></frameset> tags! However, if you add a <noframes> tag containing some text for browsers that do not support frames, you will have to enclose the text in <body></body> tags! See how it is done in the first example below.

HTML Tables

HTML Tables

Apples 44%
Bananas 23%
Oranges 13%
Other 10%

Examples

Try it Yourself - Examples

Tables
How to create tables in an HTML document.
Table borders
How to specify different table borders.
(You can find more examples at the bottom of this page).

HTML Tables

Tables are defined with the <table> tag.
A table is divided into rows (with the <tr> tag), and each row is divided into data cells (with the <td> tag). td stands for "table data," and holds the content of a data cell. A <td> tag can contain text, links, images, lists, forms, other tables, etc.

Table Example

<table border="1">
<tr>
<td>row 1, cell 1</td>
<td>row 1, cell 2</td>
</tr>
<tr>
<td>row 2, cell 1</td>
<td>row 2, cell 2</td>
</tr>
</table>
How the HTML code above looks in a browser:
row 1, cell 1 row 1, cell 2
row 2, cell 1 row 2, cell 2


HTML Tables and the Border Attribute

If you do not specify a border attribute, the table will be displayed without borders. Sometimes this can be useful, but most of the time, we want the borders to show.
To display a table with borders, specify the border attribute:
<table border="1">
<tr>
<td>Row 1, cell 1</td>
<td>Row 1, cell 2</td>
</tr>
</table>


HTML Table Headers

Header information in a table are defined with the <th> tag.
All major browsers will display the text in the <th> element as bold and centered.
<table border="1">
<tr>
<th>Header 1</th>
<th>Header 2</th>
</tr>
<tr>
<td>row 1, cell 1</td>
<td>row 1, cell 2</td>
</tr>
<tr>
<td>row 2, cell 1</td>
<td>row 2, cell 2</td>
</tr>
</table>
How the HTML code above looks in your browser:
Header 1 Header 2
row 1, cell 1 row 1, cell 2
row 2, cell 1 row 2, cell 2

HTML Images

Example

Norwegian Mountain Trip

Pulpit Rock

Try it yourself »

Examples

Try it Yourself - Examples

Insert images
How to insert images into an HTML document.
Insert images from different locations
How to insert an image from another folder or another server.
(You can find more examples at the bottom of this page).

HTML Images - The <img> Tag and the Src Attribute

In HTML, images are defined with the <img> tag. 
The <img> tag is empty, which means that it contains attributes only, and has no closing tag.
To display an image on a page, you need to use the src attribute. Src stands for "source". The value of the src attribute is the URL of the image you want to display.
Syntax for defining an image:
<img src="url" alt="some_text"/>
The URL points to the location where the image is stored. An image named "boat.gif", located in the "images" directory on "www.w3schools.com" has the URL: http://www.w3schools.com/images/boat.gif.
The browser displays the image where the <img> tag occurs in the document. If you put an image tag between two paragraphs, the browser shows the first paragraph, then the image, and then the second paragraph.

HTML Images - The Alt Attribute

The required alt attribute specifies an alternate text for an image, if the image cannot be displayed.
The value of the alt attribute is an author-defined text:
<img src="boat.gif" alt="Big Boat" />
The alt attribute provides alternative information for an image if a user for some reason cannot view it (because of slow connection, an error in the src attribute, or if the user uses a screen reader).

HTML Images - Set Height and Width of an Image

The height and width attributes are used to specify the height and width of an image.
The attribute values are specified in pixels by default:
<img src="pulpit.jpg" alt="Pulpit rock" width="304" height="228" />
Tip: It is a good practice to specify both the height and width attributes for an image. If these attributes are set, the space required for the image is reserved when the page is loaded. However, without these attributes, the browser does not know the size of the image. The effect will be that the page layout will change during loading (while the images load).

Basic Notes - Useful Tips

Note: If an HTML file contains ten images - eleven files are required to display the page right. Loading images takes time, so my best advice is: Use images carefully.
Note: When a web page is loaded, it is the browser, at that moment, that actually gets the image from a web server and inserts it into the page. Therefore, make sure that the images actually stay in the same spot in relation to the web page, otherwise your visitors will get a broken link icon. The broken link icon is shown if the browser cannot find the image.

HTML Lists

The most common HTML lists are ordered and unordered lists:

HTML Lists

An ordered list:

  1. The first list item
  2. The second list item
  3. The third list item

An unordered list:

  • List item
  • List item
  • List item

Examples

Try-It-Yourself Examples

Unordered list
How to create an unordered list in an HTML document.
Ordered list
How to create an ordered list in an HTML document.
(You can find more examples at the bottom of this page).

HTML Unordered Lists

An unordered list starts with the <ul> tag. Each list item starts with the <li> tag.
The list items are marked with bullets (typically small black circles).
<ul>
<li>Coffee</li>
<li>Milk</li>
</ul>
How the HTML code above looks in a browser:
  • Coffee
  • Milk

HTML Ordered Lists

An ordered list starts with the <ol> tag. Each list item starts with the <li> tag.
The list items are marked with numbers.
<ol>
<li>Coffee</li>
<li>Milk</li>
</ol>
How the HTML code above looks in a browser:
  1. Coffee
  2. Milk

HTML Definition Lists

A definition list is a list of items, with a description of each item.
The <dl> tag defines a definition list.
The <dl> tag is used in conjunction with <dt> (defines the item in the list) and <dd> (describes the item in the list):
<dl>
<dt>Coffee</dt>
<dd>- black hot drink</dd>
<dt>Milk</dt>
<dd>- white cold drink</dd>
</dl>