The document discusses the CSS box model which defines how elements are laid out using properties like margins, borders, padding, height and width. It describes how different browsers like Internet Explorer previously calculated box dimensions differently than other browsers, sometimes causing broken layouts. It provides workarounds like box model hacks to avoid these issues and suggests best practices like cross-browser testing.

1. Box Model By : Payel Ghosh Mail : g.payel@ puneitlabs.com

2. What is the box model Box 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

3. The box model in context

4. 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 */

5. CSS Box Model : Padding padding 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

6. 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

7. The broken Box Model Broken 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

8. 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;

9. Affects on layouts Internet 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

10. 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

11. 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