said by quatrix :

Contrary to some of the false information here (maybe from the same non-experts who preach against JavaScript and cookies, leave anti-virus and other stuff resident in memory, etc.) there's essentially no difference and nothing to worry about. If you want to see for yourself, log into a secure site, copy the URL, close the browser, reopen it, and try to load the URL. Unless the web site is seriously screwed up, you'll have to log in again.

said by Mozillazine :

Disk caching saves copies of the downloaded files on the hard drive so they doesn't need to be downloaded to be redisplayed. These pages can be viewed by anyone with permission to the cache folder.

Pages transmitted with SSL encryption often contain sensitive information and caching of these pages to disk may present a privacy risk. This preference controls whether to cache to disk pages that were transmitted with SSL encryption.

Possible values and their effects
true = Cache to disk content retrieved by SSL.

false = Don't cache to disk content retrieved by SSL. (Default)

MORE INFORMATION
When you try to open or to download an active document over SSL, you can use one the following methods to prevent permanent client-side caching. The solutions listed here only work when you try to open or to download the active document as a result of a POST request or by clicking a hyperlink on a Web page.

• Change security settings in Microsoft Internet Explorer. To do this, follow these steps:
1. On the Tools menu, click Internet Options.
2. On the Advanced tab, scroll to Security, and then click to select the Do not save encrypted pages to disk check box.
• Add a Cache-control: no-store HTTP header to the response message.
• You can also add the Cache-control: no-cache HTTP header to the response message. Currently, when you add the Cache-control: no-cache header, the download fails.
Internet Explorer must save the file to the local cache to enable the associated application to load the file. Temporary client caching of active documents has only been implemented for hyperlink or for POST request scenarios to allow the associated application to load the documents. Therefore, if you use the above methods and try to open or to download the active document directly by typing the URL of the document in the Internet Explorer Address bar, the download fails.

said by quatrix :

Contrary to some of the false information here (maybe from the same non-experts who preach against JavaScript ....