css rounded corners/code check/id or class? please

[paulmo]

trying to do rounded corners with css as mentioned here (or similar if someone can advise). able to do it with new, test file (html/css) for only one area that runs entire width of page but not able to figure it out incorporating into my existing external css (using float columns) for my site. here's my css (question follows after code--thanks for bearing with me!):body { margin: 0 5 10 5; padding: 0; color: #191970 font-size: 90%; font-family: arial, helvetica, sans-serif; background-color:#8FBC8F } #header { width: 80%; height: 5px; background-color: ; margin-bottom: 5px; margin-left: 20%; } #gutter { float: left; width: 3%; height: 1px; } #col1 { height: 500px; float: left; width: 25%; background-color: #FFFACD; margin-bottom: 10px; margin-left: 3%; } #col2 { float: left; width: 45%; background-color: #FFFACD; margin-bottom: 10px; padding: 5px; } #col3 { height: 100px; float: right; width: 20%; margin-right: 2%; padding: 1em; background-color: #FFFACD; margin-bottom: 5px; } #col4 { float: left; width: 43%; background-color: #FFF0F5; margin-bottom: 10px; margin-left: 4%; padding: 5px; } #footer { margin-bottom: 10px; margin-left: 21%; padding: .5em; float: left; width: 55%; height: 65px; background-color: ; } h1 { color: #191970; font-size: 100% margin: 0; padding: 0px; text-align: left; } h2 { font-size: 125%; color: #FFF0F5; margin-top: 0; padding-top: 3px; text-align: center; } h3 { color: #191970; text-align: center; font-size: 60%; } h4 { font-size: 100%; color: #191970; margin-top: 0; padding-top: 3px; text-align: center; } p { font: geogia; font-size: 10 pt; color: #191970; text-align: left } ul.square {list-style-type: square; color: #191970; font-size: 10 pt; text-align: left; }ul.disc {list-style-type: disc}also wondering, is there a difference/advantage to using #/ div id= in css/html or ./ div class=? seems the same to me, except when mixing/matching id/class and #/., get some unusual effects. thanks for help here

[Synook]

also wondering, is there a difference/advantage to using #/ div id= in css/html or ./ div class=? seems the same to me, except when mixing/matching id/class and #/., get some unusual effects.

Each ID can only apply to one element on a page, so if you want to have a rule apply to multiple elements you have to use classes. However, if an element already has an ID for another reason you can use the ID to refer to it instead of giving it a class attribute as well.

[paulmo]

thanks for that--finally understand it now