ทำไมคนบางอย่างของไวยากรณ์แบบ CSS ฟังก์ชันไม่ได้ทำงานของฉัน WPF WebBrowser ธาตุ?

<style>
table tr{
background-color: #494D54;
color:lightblue;
font-family: Arial, Helvetica, sans-serif;
font-weight: bolder;
}
table tr:hover{
background-color: #636873;
}
table{
  border-collapse: collapse;
  width: 100%;
}

table td{
  border: 1px solid #ddd;
  padding: 8px;
}
.lb_table_subtitle{
    padding-top: 12px;
    padding-bottom: 12px;
    text-align: left;
    background-color:#114C88;
    color: white;
}

lb_table_subtitle:hover{
    background-color:#636873;
}
table tr:nth-child(odd){background-color: #2E3136;}
body {
    background-color:#494D54;
    border-radius: 50px;
}
</style>

<table cellSpacing="0"  cellPadding="0" width="100%" class="lb_table"><tr><td colspan="2" class="lb_table_subtitle">Technische Spezifikationen</td></tr><tr><td>Prozessor</td><td>Intel Xeon</td></tr><tr><td>Prozessortyp</td><td>Xeon MP</td></tr><tr><td>Anzahl der CPUs</td><td>2</td></tr><tr><td>Anzahl der CPU-Steckplätze</td><td>4</td></tr><tr><td>Prozessortakt (MHz)</td><td>1900</td></tr><tr><td>Prozessor Cache (kb)</td><td>1024</td></tr><tr><td>Front Side Bus - FSB (MHz)</td><td>400</td></tr><tr><td>Arbeitsspeicher (GB)</td><td>1</td></tr><tr><td>Festplattentyp</td><td>SCSI</td></tr><tr><td>Grafikkarte onboard</td><td>ja</td></tr><tr><td>Sound</td><td>nein</td></tr><tr><td>Anzahl der Netzteile</td><td>2</td></tr><tr><td>Bauart</td><td>Rack</td></tr><tr><td colspan="2" class="lb_table_subtitle">Festplatten - weitere HDDs oder einzelne Rahmen auf Anfrage</td></tr><tr><td>36 GB SCSI</td><td>1</td></tr><tr><td>Gesamtkapazität (GB)</td><td>36</td></tr><tr><td>max. Festplatten</td><td>3</td></tr><tr><td colspan="2" class="lb_table_subtitle">Weitere Laufwerke</td></tr><tr><td>CD-ROM</td><td>ja</td></tr><tr><td>Diskettenlaufwerk</td><td>ja</td></tr><tr><td colspan="2" class="lb_table_subtitle">PCI-Devices onboard</td></tr><tr><td>Device_1</td><td>Ethernet Pro 100</td></tr><tr><td>Device_2</td><td>SCSI-Controller U160</td></tr><tr><td colspan="2" class="lb_table_subtitle">Erweiterungssteckplätze</td></tr><tr><td>PCI 64-bit 33MHz</td><td>1</td></tr><tr><td>PCI 64-bit 66MHz</td><td>4</td></tr><tr><td>PCI-X 133MHz</td><td>1</td></tr><tr><td colspan="2" class="lb_table_subtitle">Anschlüsse</td></tr><tr><td>VGA</td><td>1</td></tr><tr><td>Ethernet RJ45</td><td>1</td></tr><tr><td>PS/2</td><td>2</td></tr><tr><td>Serial Port</td><td>1</td></tr><tr><td>USB</td><td>3</td></tr></table>