How to read the content in taking Http to wrap

Acquire respondent parcel of a HTTP for example

It was included
HTTP/1.1200OK
Server:MIcrosoft-IIS/4.0
Date:MOn, 3Jan200513:13:33GMT
Content-Type:tExt/html
Last-Modified:MOn, 11Jan200413:23:42GMT
Content-Length:90


How do I obtain the value of Last-Modified? Not be all websites have Last-Modified
You can see the property of HttpwebresponseI now is the LastModified property that uses HttpWebResponse, but the time that wins fetch from some pages is wrong.
But I use text casing to show content of HTTP respondent bag entirely, reach similar time
Last-Modified:MOn, 11Jan200413:23:42GMT
However the majority is right.

Do not know me to keep clear of problem expression deny
Above all the browser delivers a server Last-Modified. Label file alters time finally
Again the server is delivered come back, whether does browser judgement happen revise do relative.
Because this time won't be the present time of your server, however of the file on the server edit finally timeAlter time the server is each files what I want finally namely. Did not understand upstairs meaningHead of not all Http can take Last-Modified, so you pass this this method is gotten not safeI want to be less than what method, can you say to use what method?

I am to if be worth without Last-Modified,think, this Url abandons need not. Be being carried in the client do not have method. On the server Js has an attribute to be called Lastmodixxxx
Is there method? Unlikely, after all methodical. Ah, do not believe I also do not have method