完整代码如下：
<!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" xml:lang="en" lang="en"> <head> <title>html文本框提示效果</title> <style type="text/css"> *{ margin:0px;padding:0px;font-size:12px; } input{ width:100px;height:20px;border:1px solid #ccc; } </style> </head> <body> <script language="javascript"> function tips(id,str){ var l=document.getElementById(id).offsetLeft+120; var t=document.getElementById(id).offsetTop; document.getElementById("tips").innerHTML="提示："+str; document.getElementById("tips").style.left=l+"px"; document.getElementById("tips").style.top=t+"px"; document.getElementById("tips").style.display=""; } function outtips(){ document.getElementById("tips").style.display='none'; } </script> <div id="tips" style="position:absolute;border:1px solid #ccc;padding:0px 3px;color:#f00;display:none;height:20px;line-height:20px;background:#fcfcfc"></div> <br /> 姓名：<input type="text" id="username" onfocus="tips('username','姓名长度最多16个字符')" onblur="outtips()" /> <br /> 密码：<input type="password" id="password" onfocus="tips('password','密码长度必须在3-18位之间')" onblur="outtips()" /> </body> </html>