!DOCTYPEhtmlhtmlheadtitle表单美化/titlescripttype="text/javascript"src="jquery-3.3.1.min.js"/scriptstyletype="text/css"#input_name{width:200px;height:20px;border-radius:2px;box-shadow:0px0px3px#ccc,010px15px#eeeinset;border:1pxsolid#f0f0f0;}#input_name:focus{width:200px;transition:width1slinear0s;border-color:1pxsolid#555;outline:none;/*这个是去去除本省存在的边框颜色*/background:#fffurl(images/red_asterisk.png)no-repeat98%center;box-shadow:003px#aaa;padding-right:70px;line-height:20px;position:relative;padding-right:70px;}#input_name:required:valid{/*当输入有效的时候，触发*/background:#fffurl(images/valid.png)no-repeat98%center;box-shadow:005px#5cd053;border-color:#28921f;}#input_name:focus:invalid{background:#fffurl(images/invalid.png)no-repeat98%center;box-shadow:005px#d45252;border-color:#b03535;}/*当输入无效的时候，不触发*/#input_name:required:valid+.input_text{background-color:green;}#input_name:focus+.input_text{display:inline-block;color:"#fff";text-align:center;}.input_text{background:#d45252;border-radius:3px3px3px3px;color:white;margin-left:8px;padding:1px6px;z-index:999;position:absolute;display:none;}.input_text::before{content:"25C0";/*带小箭头的*/color:#d45252;position:absolute;top:1px;left:-6px;}#input_name:focus+.input_text{display:inline;}#input_name:required:valid+.input_text{background:#28921f;}#input_name:required:valid+.input_text::before{color:#28921f;}/stylescripttype="text/javascript"$(function(){$("#input_name").bind("blur",function(){varvalue_valid=this.value;if(value_valid.length6){this.value="";}elseif(value_valid.length18){this.value="";}elseif(((value_valid.substring(0,1)='a')(value_valid.substring(0,1)='z'))||((value_valid.substring(0,1)='A')(value_valid.substring(0,1)='Z'))){return}else{this.value="";}})})/script/headbodydivclass="form_table"formaction=""method=""id="frmV"ulspan姓名/spaninputtype="text"id="input_name"requiredplaceholder="name"name="username"value=""/!----spanclass="input_text"正确格式为：6~18个字符，可使用字母、数字、下划线，需以字母开头/span/ul/form/div/body/html

1.显示箭头

ahref="javascript:;"class="arrow"id="prev"lt;/aahref="javascript:;"class="arrow"id="next"gt;/a//这段话表示javascript:;防止产生链接