//返回顶部按钮
function show_goback(page_name)
{
	if(page_name != 'index2'){
		var nav_num = 0;loc_url = location.href;
		var domain = loc_url.substring(7);
		domain = domain.substring(0, domain.indexOf('/'));
		var is_show_by_page = 0;    //是否显示按钮根据不同的页面
		var back_links = $('.mainnav .nav ul li a');
		back_links.each(function(i){
			if(loc_url.indexOf($(back_links[i]).attr('href')) == 7+domain.length) {
				nav_num = i;
				is_show_by_page = 1;
				return false;
			}
		});
		if(is_show_by_page == 0 && loc_url == 'http://'+domain+'/') {
			is_show_by_page = 1;
		}
		if(is_show_by_page == 0) {
			return false;
		}
		var re = 90;
	}else{
		var re = 240;
		is_show_by_page = 1;
	}
    var fe = $('#go_lstop');
    var top_h = $('#go_lstop').height();
    var footer_top = $('.g_footer').offset().top;
 
    if(nav_num == 0) {
        top_h -= 148; 
    }
    function fixed_goback() {
        var y = $(window).scrollTop();
        if (y < 450) {
            fe.css('display', 'none');
            fe.stop();
            fe.hide();
            return false;
        } else {
            fe.fadeIn();
        }

        var top, ua = get_navigator();
        var h = $(window).height() - re;
        if (ua == 'ie6') {
            if (footer_top <= y + h + top_h) {
                top = footer_top - top_h - 25;
            } else {
                top = y + h;
            }
        } else {
            if (footer_top <= y + h + top_h) {
                top = footer_top - y - top_h - 25;
            } else {
                top = h;
                if (top < 0) {
                    top = 10;
                }

            }
        }
        var window_width = $(window).width();

        var left = (window_width + 996) / 2;
        
        fe.css('display', 'block');
        fe.css('top', top + 'px');
        fe.css('margin-left', left+'px');

    }
    $(window).scroll( function(){fixed_goback();} );
    $(window).resize( function(){fixed_goback();} );
}


//返回浏览器版本
function get_navigator() {
    var ua = navigator.userAgent.toLowerCase();
    if (ua.indexOf('msie 6.0') > -1) {
        return 'ie6';
    } else if (ua.indexOf('firefox') > -1) {
        return 'firefox';
    }
    return false;
}