Alguien podría explicar esto

[Developer9]

Código:

<style type="text/css">
.text_header {
color: #FF99FF;
font: 20px "Courier New", Courier, mono;
font-weight: bold;
letter-spacing:1px;
/*border:3px groove blue;*/
padding: 0px 4px 0px 100px;
border-right:1px solid #CCCCCC;
border-bottom: 1px solid #CCCCCC;
background: #333333;
}
.bg_content{
background-image: url(cassette_1.jpg);
background-repeat:repeat;
}
.box_profile_info_small_heading,.box_profile_info_large_heading{
font: 20px "Courier New", Courier, mono;
letter-spacing:-3px;
color: #0066FF;
}
.box_profile_info_large_heading{
font: 18px Lucida Console, Monaco, monospace;
letter-spacing:-4px;
color: #FF3399;

}
.box_profile_info_small_content,.box_profile_info_large_content{
font:14px Palatino Linotype, Book Antiqua, Palatino, serif ;
font-weight:bold;
color: #3300FF;
letter-spacing:3px;
}
.bg_network{
background-color: #999999;
}
a, a:visited, a:active,a.link_blue {
color: #00FF00;
font: 12px Verdana, Arial, Helvetica, sans-serif;
font-weight: bold;
text-decoration:overline;
border-bottom:1px solid #009900;
}
.box_content_profile_groups, .box_content_profile_journal {
background-image: url(subBgkd3.gif);
background-repeat: repeat-x;
background-position:top left;
}
.box_content_profile_friends {
background: none;
background-color:transparent;
}
.text_journal_entry_body {
background-color:transparent;
font: 12px "Courier New", Courier, mono;
}
.bg_border {
border: 1px solid #666666;
}
.bg_title {
background-color: #666666;
}
.bg_title span.text_header {
padding-left: 150px;
font-size:40px;
letter-spacing:-1px;
font-family: "Times New Roman", Times, serif;
border-right:1px solid #000000;
border-bottom: 1px solid #000000;
background: #999999;
}
</style>