HTTP缓存头Last-Modified和ETag介绍
第一次请求
请求：
GET/pic/201408/102.jpgHTTP/1.1 Host:www.nhooo.com Connection:keep-alive Cache-Control:no-cache Accept:image/webp,*/*;q=0.8 Pragma:no-cache User-Agent:Mozilla/5.0(WindowsNT6.1)AppleWebKit/537.36(KHTML,likeGecko)Chrome/29.0.1547.66Safari/537.36 Referer:https://www.nhooo.com/ Accept-Encoding:gzip,deflate,sdch Accept-Language:zh-CN,zh;q=0.8
响应：
HTTP/1.1200OK Content-Length:66529 Content-Type:image/jpeg Last-Modified:Tue,19Aug201412:23:54GMT Accept-Ranges:bytes ETag:"029e570a8bbcf1:1ae2" Server:Microsoft-IIS/6.0 X-Powered-By:ASP.NET Date:Wed,20Aug201400:29:03GMT
xxx