Most of the differences between Quirks Mode and Strict mode are highlighted below: If you want to get more information and a deeper understanding of the subject please visit this following website:
http://www.quirksmode.org/css/quirksmode.html
Quirks Mode is for old rules (older Browsers) while Strict Mode is for standard rules (Newer Browsers). Most Modern Browsers support both modes for backwards compatibility reasons but older browsers only support the Quirks mode by default and moderns rules will not work on older browsers. If no DOCTYPE is specified older browsers and newer browsers will process the page in quirks mode. Here is what the DOCTYPE looks like <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
The moral of the story is not to use older codes with new DOCTYPES. If your old Javascritpt menus are not working the way they are supposed to, your problem may be related to the DOCTYPE that you are using.
DOCTYPE
http://www.w3.org/QA/2002/04/valid-dtd-list.html
Quirks Mode Wikipedia
http://en.wikipedia.org/wiki/Quirks_mode
Quirks mode and strict mode
http://www.quirksmode.org/css/quirksmode.html
Compatibility Chart
http://www.quirksmode.org/css/contents.html


. Note If the check box has a gray background, click Form Field Shading
on the Forms toolbar to remove the gray shading.
Click the next cell where you want to insert a check box, and then press CTRL+Y to insert another check box.
After you insert a check box for each item that you want, click the top right cell and type the text for the first item. Repeat this step for each item in the list."