hello,
select does not has an event for onclick, try onchange like this
<select id="Select1" name="shortcut" class="sl" style="margin-left: 10px">
<option selected="selected">Select Language</option>
<option onchange="window.open('multi_language.htm','Multi Language','width=500,height=400,left=250,top=100,screenX=100,screenY=100')">
Belarusian</option>
<option onchange="window.open('multi_language.htm','Multi Language','width=500,height=400,left=250,top=100,screenX=100,screenY=100')">
Bulgarian</option>
<option onchange="window.open('multi_language.htm','Multi Language','width=500,height=400,left=250,top=100,screenX=100,screenY=100')">
German</option>
<option onchange="window.open('multi_language.htm','Multi Language','width=500,height=400,left=250,top=100,screenX=100,screenY=100')">
English</option>
</select>
hope this will help you.