$(function(){
			//判断是否是手机
			var mobile_flag = isMobile();
			if(!mobile_flag){
				$("body").css("margin","0 25%");
			}
		});
		function isMobile() {
			var userAgentInfo = navigator.userAgent;

			var mobileAgents = [ "Android", "iPhone", "SymbianOS", "Windows Phone", "iPad","iPod"];

			var mobile_flag = false;

			//根据userAgent判断是否是手机
			for (var v = 0; v < mobileAgents.length; v++) {
				if (userAgentInfo.indexOf(mobileAgents[v]) > 0) {
					mobile_flag = true;
					break;
				}
			}
			var screen_width = window.screen.width;
			var screen_height = window.screen.height;

			//根据屏幕分辨率判断是否是手机
			if(screen_width < 500 && screen_height < 800){
				mobile_flag = true;
			}
			return mobile_flag;
		}

转载：https://www.cnblogs.com/dalaowang/p/10315419.html