I have the following html. It’s nothing fancy. It just creates a list of items vertically. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Demos</title> <style> #idList { margin: 0; padding: 0; } #idList li { display: block; margin: 0; padding: 4px; width: 120px; background: #333; color: #888; } </style> </head> <body> <ul id="idList"> <li>option 1</li> <li>option 2</li> <li>option 3</li> <li>option 4</li> <li>option 5</li> <li>option 6</li> <li>option 7</li> <li>option 8</li> <li>option 9</li> <li>option A</li> <li>option B</li> <li>option C</li> <li>option D</li> <li>option E</li> <li>option F</li> </ul> </body> </html> Code (markup): But if I add the font type font: normal 13px Courier; Code (markup): like the following <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Demos</title> <style> #idList { margin: 0; padding: 0; } #idList li { display: block; margin: 0; padding: 4px; width: 120px; background: #333; color: #888; font: normal 13px Courier; } </style> </head> <body> <ul id="idList"> <li>option 1</li> <li>option 2</li> <li>option 3</li> <li>option 4</li> <li>option 5</li> <li>option 6</li> <li>option 7</li> <li>option 8</li> <li>option 9</li> <li>option A</li> <li>option B</li> <li>option C</li> <li>option D</li> <li>option E</li> <li>option F</li> </ul> </body> </html> Code (markup): IE6 creates lines between these items. Why is this happening and how can I fix this?