Menu Drop Down CSS

Primeiro Vá em Model >> Editar HTML >> Expandir Widgets >> Procure por: 

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Logo acima dessa tag cole o seguinte código:

/* NavbarMenu
--------------------------- */
#NavbarMenu {
background: #555 url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPXX_Yo-wUo6cT5RzAALCW-PLIzP8yDZ5ZEYKZ_0We1YA5aZokckIbCxOaNChxohRmFzaRj_uM9IzFjZ_GAF0HK2U4UEQn-XcUvkoSoFQdyk92nO8t7n4_4pK_zfeT54-QbhK2WhE3Lww/s1600/navbar.png);
width: 100%;height: 35px;
font-size: 12px;
font-family: Arial, Tahoma, Verdana;
color: #FFF;/*--cor do link--*/
font-weight: bold;margin: 0;padding: 0;text-transform: capitalize;
}
#NavbarMenuleft {
width: 100%;float: left;margin: 0;padding: 0;
}
#nav {
margin: 0;
padding: 0;
}
#nav ul {
float: left;list-style: none;margin: 0;padding: 0;
}
#nav li {
list-style: none;margin: 0;padding: 0;
}
#nav li a, #nav li a:link, #nav li a:visited {
color: #FFF; /*--edite cor do link--*/
display: block;
font-size: 16px;/*--tamanho da fonte do link--*/
font-family: Georgia, Times New Roman;font-weight: normal;text-transform: capitalize;
margin: 0;padding: 9px 15px 8px;border-right: 1px solid #fff;
}
#nav li a:hover, #nav li a:active {
background: #555 url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiHGeDw3BJvh1o6DOFcovFzVWmBafpdR46hVmgyssnmP_CzToJKumEqhyGAVTlSt46HO5kYJANdSjvzLbTKzcZojuoc6ng1cAro-jKLVN4yRcZH8p-xZE02-IQTV-27dR1VRDxK4V95v2w/s1600/navhov.png);
color: #FFF;  /*--edite cor do link hover--*/
margin: 0;padding: 9px 15px 8px;text-decoration: none;
}
#nav li li a, #nav li li a:link, #nav li li a:visited {
background: #555;/*--cor de fundo--*/
width: 150px;
color: #FFF; /*--cor do link--*/
font-size: 14px;font-family: Georgia, Times New Roman;font-weight: normal;text-transform: capitalize;
float: none;margin: 0;padding: 7px 10px;border-bottom: 1px solid #FFF;border-left: 1px solid #FFF;border-right: 1px solid #FFF;
}
#nav li li a:hover, #nav li li a:active {
background: #777;/*--cor de fundo hover--*/
color: #FFF; /*--cor do link--*/
padding: 7px 10px;
}
#nav li {float: left;padding: 0;
}
#nav li ul {z-index: 9999;position: absolute;left: -999em;height: auto;width: 170px;margin: 0;padding: 0;
}
#nav li ul a {width: 140px;
}
#nav li ul ul {margin: -32px 0 0 171px;}
#nav li:hover ul ul, #nav li:hover ul ul ul, #nav li.sfhover ul ul, #nav li.sfhover ul ul ul {
left: -999em;}
#nav li:hover ul, #nav li li:hover ul, #nav li li li:hover ul, #nav li.sfhover ul, #nav li li.sfhover ul, #nav li li li.sfhover ul {left: auto;}
#nav li:hover, #nav li.sfhover {position: static;}

Agora para instalar é facil, adicone um gadget HTML/JavaScript, e cole editando os nomes e os links

<div id='NavbarMenu'>
<div id='NavbarMenuleft'>
<ul id='nav'>
<li><a expr:href='data:blog.homepageUrl'>Home</a></li>
<li>
<a href='ENDEREÇO DO SEU LINK AQUI'>Link 1</a>
<ul>
<li><a href='ENDEREÇO DO SEU SUBLINK AQUI'>Sub Link #1.1</a></li>
<li><a href='ENDEREÇO DO SEU SUBLINK AQUI'>Sub Link #1.2</a></li>
<li><a href='ENDEREÇO DO SEU SUBLINK AQUI'>Sub Link #1.3</a></li>
<li><a href='ENDEREÇO DO SEU SUBLINK AQUI'>Sub Link #1.4</a></li>
<li><a href='ENDEREÇO DO SEU SUBLINK AQUI'>Sub Link #1.5</a></li>
</ul>

Créditos a Design on Storm*