这有效,提供间距和其他格式选项。上述接受的选项不起作用
<div runat="server" class="tooltip" id="divHowTo" style="display: inline-block; width:75px" data-tip="If you have problems: 

1.) Enter a users id 

2.) Choose a corresponding domain for the pin 

3.) Verify resolved name is correct 

4.) (If adding) Browse for Picture (jpg/png format) (square resolution) (240px X 240px or larger) 

5.) Choose a button to add or delete or view or save or clear " >
<asp:Image ID="imgHowTo" runat="server" ImageUrl="Images/howTo1s.jpg" Height="73px" Width="73px"/>
</div>
与(在 <style> 和 </style> 之间)的类
.tooltip {
display:inline-block;
width:64px;
height:64px;
position:relative;
margin:25px;
background-repeat: no-repeat;
background-position:50% 50%;
background-size:100%;
text-align:center;
line-break:auto;
white-space:pre-line;
}
.tooltip:hover:after {
display:inline-block;
position:absolute;
top:-25px;
left:50%;
height:400px;
content: attr(data-tip);
font:bold 10px/14px Arial, sans-serif;
background:#f0f0f0;
color:#333;
white-space:pre-line;
border:1px solid #665;
padding:2px 4px;
width:150px;
margin:0 0 0 -75px;
border-radius:3px;
line-break:auto;
}
.tooltip:hover:before {
border-top: 10px solid #665;
border-top: 10px solid #665;
margin-top: 5px;
content: "";
position: absolute;
border-left: 5px solid transparent;
border-right: 10px solid transparent;
top:-15px;
left: 50%;
margin-left: -10px;
line-break:auto;
white-space:pre-line;
}