Background color changes when the mouse passes

<Style type = "text/CSS">
# Coolmenu {
Border: 1px solid black;
Border-bottom-width: 0;
Width: 170px;
Background-color: # e6e6e6;
}
* Html # coolmenu {
Width: 164px;
}
# Coolmenu {
Font: bold 13px verdana;
Padding: 2px;
Padding-left: 4px;
Display: block;
Width: 100%;
Color: black;
Text-Decoration: none;
Border-bottom: 1px solid black;
}
HTML> body # coolmenu {
Width: auto;
}
# Coolmenu A: hover {
Background-color: black;
Color: white;
}
</Style>
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<Div id = "coolmenu">
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