Box Model By : Payel Ghosh

Mail : g.payel@puneitlabs.com

What is the box modelBox model defines contents inside an HTML element as being surrounded by an invisible rectangular box, surrounding this box are three rectangular belts, represented by the margin, border, and padding properties.

Describing box model is the manipulation of a block-level element through:

• Margin• Border• Padding• Height• Width

The box model in context

CSS Box Model : Margins• margin

Values: [ <length> | <percentage> | auto ]{1,4} |

Initial value: Not defined

Applies to: All elements

Inherited: No

Percentages: Refer to the width of the containing block

Computed value: See individual properties

• Margin properties: margin-top, margin-right, margin-bottom,

margin-left, margin;

example:

BODY { margin: 2px } /* all margins set to 2px */

BODY { margin: 1px 2px } /* top & bottom = 1px, right & left = 2px */

BODY { margin: 1px 2px 3px } /* top=1px, right=2px, bottom=3px, left=2px */

CSS Box Model: Paddingpadding

• Values: [ <length> | <percentage> ] {1,4}• Initial value: Not defined for shorthand elements• Applies to: All elements• Inherited: No• Percentages: Refer to the width of the containing block• Computed value: See individual properties (padding-top, etc.)

• Note: Padding should never be negative

CSS Box Model: Border

Border :

• Values: [ none | hidden | dotted | dashed | solid | double | groove | ridge | inset | outset ]{1,4} |

• Initial value: Not defined for shorthand properties• Applies to: All elements• Inherited: No

The broken Box ModelBroken layouts

• The broken box model occurs in internet explorer

• Widths of block-level elements ( div, p, h1 etc) will be different to other browsers like Mozilla, Opera, Safari

• Your layout may work in one browser , but be broken in another

Calculating the Box Model• Web Standards Calculation

– Width deals with content only. Padding and border and margin are set in addition to the width.

– Box of 100px with padding: 10px; border: 10px need a width: 100px;

• IE 5 (all modes) IE 6/7 quirks mode– Width deals with entire box model. Padding, and border are

contained within the width.– Box of 100px with padding: 10px; border: 10px

need a width: 140px;

Affects on layoutsInternet explorer – the culprit• Calculates widths and heights differently• IE 5/6/7 are affected

Quirks mode• IE 6 and 7 will revert if you do not specify a DOCTYPE• DOCTYPE needs to be first line in HTML document• IE still reverts even after mentioning DOCTYPE

Avoidance Tactics Box model problems can be avoided by:• staying aware of the problems and fixes• Cross-browser testing

some tricks• Not to apply margin or padding to a div in order to create space in a

layout.• Apply margins or padding to the elements inside the div

The Box Model Hacks

• Box-in-box• The Tantek Hack• Simplified Box Model Hack (SBMH)• A modified SBMH• Alternate Box Model Hack• advantages and disadvantages

Follow the link :

http://css-discuss.incutio.com/?page=BoxModelHack