CSS实现的表单提示效果

效果图为：

代码如下：点击运行，可预览效果

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
 <title>Form field hints with CSS and JavaScript</title>
<style type="text/css">

/* All form elements are within the definition list for this example */
dl {
 font:normal 12px/15px Arial;
    position: relative;
    width: 350px;
}
dt {
    clear: both;
    float:left;
    width: 130px;
    padding: 4px 0 2px 0;
    text-align: left;
}
dd {
    float: left;
    width: 200px;
    margin: 0 0 8px 0;
    padding-left: 6px;
}

/* The hint to Hide and Show */
.hint {
    display: none;
    position: absolute;
    right: -250px;
    width: 200px;
    margin-top: -4px;
    border: 1px solid #c93;
    padding: 10px 12px;
    /* to fix IE6, I can't just declare a background-color,
    I must do a bg image, too!  So I'm duplicating the pointer.gif
    image, and positioning it so that it doesn't show up
    within the box */
    background: #ffc url("/web/UploadFiles/200808/20080803220037842.gif") no-repeat -10px 5px;
}
/* The pointer image is hadded by using another span */
.hint .hint-pointer {
    position: absolute;
    left: -10px;
    top: 5px;
    width: 10px;
    height: 19px;
    background: url("/web/UploadFiles/200808/20080803220037842.gif") left top no-repeat;
}
</style>
<script type="text/javascript">
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}
function prepareInputsForHints() {
 var inputs = document.getElementsByTagName("input");
 for (var i=0; i<inputs.length; i++){
  // test to see if the hint span exists first
  if (inputs[i].parentNode.getElementsByTagName("span")[0]) {
   // the span exists!  on focus, show the hint
   inputs[i].onfocus = function () {
    this.parentNode.getElementsByTagName("span")[0].style.display = "inline";
   }
   // when the cursor moves away from the field, hide the hint
   inputs[i].onblur = function () {
    this.parentNode.getElementsByTagName("span")[0].style.display = "none";
   }
  }
 }
 // repeat the same tests as above for selects
 var selects = document.getElementsByTagName("select");
 for (var k=0; k<selects.length; k++){
  if (selects[k].parentNode.getElementsByTagName("span")[0]) {
   selects[k].onfocus = function () {
    this.parentNode.getElementsByTagName("span")[0].style.display = "inline";
   }
   selects[k].onblur = function () {
    this.parentNode.getElementsByTagName("span")[0].style.display = "none";
   }
  }
 }
}
addLoadEvent(prepareInputsForHints);
</script>
</head>
<body>
<p style="font:normal 12px/15px Arial;">Tab or click through the fields to reveal the hints.</p>
<dl>
 <dt>
  <label for="firstname">First Name:</label>
 </dt>
 <dd>
  <input
   name="firstname"
   id="firstname"
   type="text" />
  <span class="hint">This is the name your mama called you when you were little.<span class="hint-pointer"> </span></span>
 </dd>
 <dt>
  <label for="lastname">Last Name:</label>
 </dt>
 <dd>
  <input
   name="lastname"
   id="lastname"
   type="text" />
  <span class="hint">This is the name your sergeant called you when you went through bootcamp.<span class="hint-pointer"> </span></span>
 </dd>
 <dt>
  <label for="email">Email:</label>
 </dt>
 <dd>
  <input
   name="email"
   id="email"
   type="text" />
  <span class="hint">The thing with the @ symbol and the dot com at the end.<span class="hint-pointer"> </span></span>
 </dd>
 <dt><label for="year">Birth Year:</label></dt>
 <dd>
  <select id="year" name="year">
   <option value="">YYYY</option>
   <option value="1066">1066</option>
   <option value="1492">1492</option>
   <option value="1776">1776</option>
   <option value="1812">1812</option>
   <option value="1917">1917</option>
   <option value="1942">1942</option>
   <option value="1999">1999</option>
  </select>
  <span class="hint">Pick a famous year to be born in.<span class="hint-pointer"> </span></span>
 </dd>
 <dt>
  <label for="username">Username:</label>
 </dt>
 <dd>
  <input
   name="username"
   id="username"
   type="text" />
  <span class="hint">Between 4-12 characters.<span class="hint-pointer"> </span></span>
 </dd>
 <dt>
  <label for="password">Password:</label>
 </dt>
 <dd>
  <input
   name="password"
   id="password"
   type="password" />
  <span class="hint">Between 5-13 characters, but not 7.  Never 7.<span class="hint-pointer"> </span></span>
 </dd>
 <dt class="button"> </dt>
 <dd class="button">
  <input
   type="submit"
   class="button"
   value="Submit" />
 </dd>
</dl>

</body>
</html>

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