登录惯用的js

        <input type="text" class="inputstyle" maxlength="50" autocomplete="off" 
            value="请输入用户名"  
            onfocus="if(this.value=='请输入用户名') this.value='';
            this.className='inputstylefocus';return true;"
            onblur="if(this.value=='') this.value='请输入用户名';
            this.className='inputstyle';return true;">
            
        <input type="password" class="inputstyle" maxlength="20" 
            value="+_-_-_+"  
            onfocus="if(this.value=='+_-_-_+') this.value='';
            this.className='inputstylefocus';return true;"
            onblur="if(this.value=='') this.value='+_-_-_+';
            this.className='inputstyle';return true;">