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Back Button Causes a GET Request Instead of Using the Cache
Symptoms
When you click the Back button in Internet Explorer to view a previously-loaded ASP page, network activity may occur. This symptom may occur although you are using the default cache settings. This symptom is not consistent with the behavior that is described in the following Microsoft Knowledge Base article:
Q263070 How Internet Explorer Cache Settings Affect Web Browsing
Partial text from Q263070:
If you select this setting ("Check for newer versions of stored pages" set to "Automatically"), Internet Explorer checks for new content only when you return to a page that you viewed in an earlier session of Internet Explorer or on an earlier day.
Cause
This problem may occur if the page you are viewing hosts either:
An ATL DHTML control.
The WebBrowser control. This is the ATL DHTML control that hosts the WebBrowser control.
When the WebBrowser control is initialized, the "Session Start Time" is re-initialized to the current time. When you click the Back button, Internet Explorer tries to retrieve the previous page from the cache. Although the previous page is in the cache, it is treated as an expired page because the time stamp for the cached entry is older than the "Session Start Time".
Workaround
To work around this problem and prevent a reload of the ASP page, use the "response.expires" method.
IMPORTANT: After you use this workaround, the ASP page is read from the cache until it has expired.
How Internet Explorer Cache Settings Affect Web Browsing
Description of the Cache Settings
There are four options under Check for newer versions of stored pages:
Every visit to the page: When you return to a page you viewed previously, Internet Explorer should check to see whether the page changed since you last viewed it. If the page has changed, Internet Explorer displays the new page and stores it in the Temporary Internet Files. Note that selecting this option can slow down browsing between pages you have already viewed.
Every time you start Internet Explorer: When you view a Web site that you have visited before in the same Internet Explorer session, Internet Explorer uses the cached temporary Internet files instead of downloading the page. If you press F5 or click Refresh, Internet Explorer downloads the page.
Automatically (Internet Explorer 5 and later only): This is the same as the previous setting, but with a logic algorithm to understand the habits of Web page behavior. This setting specifies that when you return to a page you viewed previously, Internet Explorer should not check to see whether the page has changed since you last viewed it.
If you select this setting, Internet Explorer checks for new content only when you return to a page that you viewed in an earlier session of Internet Explorer or on an earlier day. Over time, if Internet Explorer determines that images on the page are changing infrequently, it checks for newer images even less frequently.
Never: Internet Explorer does not check the Web server for newer content.
©MSDN
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