兼容IE8以下浏览器input表单属性placeholder不能智能提示功能，以及使用jquery.validate.js表单验证插件的问题处理

// 兼容IE8以下浏览器input不能智能提示功能
    if(navigator.appName == "Microsoft Internet Explorer" && (navigator.appVersion.match(/7./i)=="7." || navigator.appVersion.match(/8./i)=="8." || navigator.appVersion.match(/6./i)=="6." || navigator.appVersion.match(/5./i)=="5.")){
        $(‘input[type=text]‘).each(function(index, val) {
            var input = $(this);
             if(input.attr(‘placeholder‘)!=‘‘){
                var def_val = input.attr(‘placeholder‘)
                var def_color = input.css(‘color‘)  // 默认表单原有颜色
                var tip_color = ‘#999‘  // 提示信息的颜色
                input.css(‘color‘,tip_color)
                input.val(def_val)
                input.on(‘focus‘, function(event) {
                    input.css(‘color‘,def_color)
                    if(input.val() == def_val){
                        input.val(‘‘)
                    }
                });
                input.on(‘blur‘, function(event) {
                    if(input.val() == ‘‘ || input.val() == def_val){
                        input.css(‘color‘,tip_color)
                        input.val(def_val)
                    }
                });
             }
        });
    } 

        // http://docs.jquery.com/Plugins/Validation/Methods/required
        required: function( value, element, param ) {
            // check if dependency is met
            if ( !this.depend(param, element) ) {
                return "dependency-mismatch";
            }
            if ( element.nodeName.toLowerCase() === "select" ) {
                // could be an array for select-multiple or a string, both are fine this way
                var val = $(element).val();
                return val && val.length > 0;
            }
            if ( this.checkable(element) ) {
                return this.getLength(value, element) > 0;
            }
            return ( $.trim(value).length > 0 ) && ( $.trim(value) != $(element).attr(‘placeholder‘) ); // 添加验证其value值不能等于placeholder值
        }