我有一个下拉菜单按钮，仅在屏幕太小时显示。我需要将它向右对齐，但float:right;不起作用。
这是CSS：
#cssmenu ul,
#cssmenu li,
#cssmenu span,
#cssmenu a {
margin: 0;
padding: 0;
position: relative;
}
#cssmenu {
height: 49px;
border-radius: 5px 5px 0 0;
-moz-border-radius: 5px 5px 0 0;
-webkit-border-radius: 5px 5px 0 0;
background: #fefefe;
background: -moz-linear-gradient(top, #fefefe 0%, #eee9f0 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #fefefe), color-stop(100%, #eee9f0));
background: -webkit-linear-gradient(top, #fefefe 0%, #eee9f0 100%);
background: -o-linear-gradient(top, #fefefe 0%, #eee9f0 100%);
background: -ms-linear-gradient(top, #fefefe 0%, #eee9f0 100%);
background: linear-gradient(top, #fefefe 0%, #eee9f0 100%);
border-bottom: 2px solid #ffffff;
width: auto;
display:block;
}
#cssmenu:after,
#cssmenu ul:after {
content: '';
display: block;
clear: both;
}
#cssmenu a {
background: #fefefe;
background: -moz-linear-gradient(top, #fefefe 0%, #ececec 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #fefefe), color-stop(100%, #ececec));
background: -webkit-linear-gradient(top, #fefefe 0%, #ececec 100%);
background: -o-linear-gradient(top, #fefefe 0%, #ececec 100%);
background: -ms-linear-gradient(top, #fefefe 0%, #ececec 100%);
background: linear-gradient(top, #fefefe 0%, #ececec 100%);
color: #000;
display: inline-block;
font-family: Helvetica, Arial, Verdana, sans-serif;
font-size: 12px;
line-height: 49px;
padding: 0 20px;
text-decoration: none;
}
#cssmenu ul {
list-style: none;
}
#cssmenu > ul {
float: left;
}
#cssmenu > ul > li {
float: left;
}
#cssmenu > ul > li > a {
color: #000000;
font-size: 12px;
}
#cssmenu > ul > li:hover:after {
content: '';
display: block;
width: 0;
height: 0;
position: absolute;
left: 50%;
bottom: 0;
/* Stile con freccia bassa
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-bottom: 10px solid #ffffff;
*/
margin-left: -10px;
}
#cssmenu > ul > li:first-child > a {
border-radius: 5px 0 0 0;
-moz-border-radius: 5px 0 0 0;
-webkit-border-radius: 5px 0 0 0;
}
#cssmenu > ul > li.active:after {
content: '';
display: block;
width: 0;
height: 0;
position: absolute;
left: 50%;
bottom: 0;
/* Stile con freccia bassa
border-left: 10px solid transparent;
border-right: 10px solid transparent;
border-bottom: 10px solid #ffffff;
*/
margin-left: -10px;
}
#cssmenu > ul > li.active > a {
-moz-box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
-webkit-box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
background: #ececec;
background: -moz-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #ececec), color-stop(100%, #ffeeff ef));
background: -webkit-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -o-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -ms-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
}
#cssmenu > ul > li:hover > a {
background: #ececec;
background: -moz-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #ececec), color-stop(100%, #ffeeff ef));
background: -webkit-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -o-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: -ms-linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
background: linear-gradient(top, #ececec 0%, #ffeeff ef 100%);
-moz-box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
-webkit-box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.1);
}
#cssmenu .has-sub {
z-index: 2;
}
#cssmenu .has-sub:hover > ul {
display: block;
}
#cssmenu .has-sub ul {
display: none;
position: absolute;
width: 200px;
top: 100%;
left: 0;
}
#cssmenu .has-sub ul li {
*margin-bottom: -1px;
}
#cssmenu .has-sub ul li a {
background: #ffffff;
border-bottom: 1px dotted #ffffff;
filter: none;
font-size: 11px;
display: block;
line-height: 120%;
padding: 10px;
color: #000000;
}
#cssmenu .has-sub ul li:hover a {
background: #e6e6e6;
}
#cssmenu .has-sub .has-sub:hover > ul {
display: block;
}
#cssmenu .has-sub .has-sub ul {
display: none;
position: absolute;
left: 100%;
top: 0;
}
#cssmenu .has-sub .has-sub ul li a {
background: #e6e6e6;
border-bottom: 1px dotted #ffffff;
}
#cssmenu .has-sub .has-sub ul li a:hover {
background: #d9d9d9;
}
仅当我添加时对齐才有效，right:-50px但这不是一个安全的解决方案。