css submenu พอชี้ไปเมนูที่มี sub แล้วพอจะชี้ไปที่ sub ยังไม่ทันชี้มันก็หายไปเลยครับ

#leftcontent{width:200px; margin-right:20px; float:left}
#leftcontent .menu{width:180px; padding:10px; float:left; margin-bottom:7px; background-color:#d79b9f; color:#9c2e35; text-decoration:none; display:block}
#leftcontent .menu:hover{background:#b63039; color:#FFFFFF; text-decoration:none}
.font16{font-size:16px; font-weight:bold}

li.submenu { list-style:none; }
li.submenu > ul { display:none; margin:0px; padding:10px; }
li.submenu:hover > ul { display:block;	width:150px; }
li.submenu > ul > li { display:block; width:180px; background-color:#d79b9f; color:#9c2e35; text-decoration:none;  float:left; padding:10px; margin-bottom:7px; }
li.submenu > ul > li:hover { width:180px; float:left; text-decoration:none; display:block; background:#b63039; color:#FFFFFF; text-decoration:none; padding:10px; margin-bottom:7px; }

<div id="leftcontent">
	<a href="#" class="menu"><span class="font16">ทดสอบ1</span><br></a>
	
	<li class="submenu"><a href="#" class="menu"><span class="font16">ทดสอบ sub</span></a>
		<ul>
			<li><a href="#">sub1</a></li>
			<li><a href="#">sub2</a></li>
			<li><a href="#">sub3</a></li>
			<li><a href="#">sub4</a></li>
		</ul>
	</li>
</div>