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Putting the Cache to Work

To take full advantage of the cache's benefits, you need to do some configuring. To configure the cache in Netscape Navigator 2 or 3, choose Options, Network Preferences, and then click the Cache tab. In Navigator 4 and later, select Edit, Preferences, and then open the Advanced category and click the Cache subcategory. Figure 3.2 shows Netscape's cache information.

Figure 3.2 You have several options when setting up Netscape's cache.


Depending to some degree on the operating system you use, the file extension of the HTML Web files might be .htm or .html. Originally, the Web was developed using UNIX computers, and Web files had the extension .html. Later, when Windows 3.1 machines started appearing on the Web, the .htm extension came into use because Windows 3.1 could work only with three-character file extensions, and many people were creating Web pages in Windows. Today, you'll see both extensions. Even though Windows 95 and 98 can accept four-letter extensions, not all Windows HTML-editing programs can, so people are still creating files with three-letter extensions; and many Windows users have simply become accustomed to three-character file extensions.

Configure any of the available settings to meet your needs:

  • Memory Cache You can tell Netscape how much of your computer's memory you want to assign to the cache. Netscape stores a few documents in the memory so that it can retrieve them extremely quickly. The button to the right of this option enables you to remove all the pages from the memory cache.

  • Disk Cache You can also tell Netscape how large the disk cache should be—that is, how much of your disk space you want to give to Netscape. How much should you give? That all depends on how much disk space you have free. (I always say that you can never have too much hard disk space, money, or beer; I've been proven wrong once or twice, though.) The button to the right of this option enables you to clear out the disk cache, which is handy when you finally run out of disk space.

  • Disk Cache Folder You can tell Netscape where to place the disk cache. If you have several hard disks, put the cache on the fastest disk or the one with the most room.

The Hard Disk Cache

Note that you are not reserving an area of your hard disk for the cache. For instance, if you have a 30,000KB (almost 30MB) disk cache, your browser doesn't create a 30,000KB file that prevents other programs from using that disk space. You're just telling the browser that it can use up to that much disk space for the cache if it's available—if other programs don't use up the space first. When you fill up the available cache space, the browser starts clearing out older files to make way for newer ones.

  • Document in Cache Is Compared to Document on Network Now for the complicated one. This setting tells Netscape when to verify documents. When you request a document (by clicking a link or entering a URL), Netscape can send a message to the Web server asking (basically), "Has this document changed since the last time I grabbed it?" If it has changed, Netscape downloads a new copy. If it hasn't changed, Netscape grabs the page from the cache. You can configure Netscape to ask the Web server to verify documents Once per Session (in which case, Netscape checks the first time you try to retrieve a document, but it doesn't bother after that); Every Time (so that Netscape checks every time you try to get a document, regardless of how many times you view that document in a session); or Never (in which case, Netscape doesn't even bother to check to see whether the document has been updated, unless you use the Reload command).

  • Allow Persistent Caching of Pages Retrieved Through SSL This feature is in earlier versions of Netscape (it's not in the latest versions), and it's related to Internet security. SSL stands for secure sockets layer (which probably means no more to you than SSL, so I'm not sure why I told you that). An SSL Web browser can use secure transmission of information; the information is encrypted before being transmitted. (See Chapter 18, "Staying Safe on the Internet," for a discussion of encryption.) This feature tells the browser to cache pages that were sent in a secure manner.

Internet Explorer 5 uses a similar system. Choose Tools, Internet Options, and click the General tab. (As you may have noticed by now, Microsoft has to keep moving things around; in some versions of Explorer you'll need to select View, Options—or perhaps Internet Options—then click the General Tab, or maybe the Advanced tab.) Then, click the Settings button under the Temporary Internet files area. Although Explorer's programmers (ever the innovators) have taken to referring to the cache as Temporary Internet files, it's the same thing. Figure 3.3 shows Explorer 5.5's settings.

Figure 3.3 Internet Explorer enables you to modify the cache and view its contents directly.

Near the top of the box, you can tell the browser when to check to see whether there's a newer version of the file. You can tell it to check Once per Session in Explorer 3; this option is ambiguously labeled Every Time You Start Internet Explorer in Explorer 4 and 5, but it's the same thing. Or, you can turn it off altogether (select Never). In Explorer 4 and 5, you also have the option to check Every Visit to the Page. And Explorer 5 has yet another option, Automatically. This starts off working the same as Every Time You Start Internet Explorer, but, in theory, the browser learns how often a particular page changes, and if it doesn't change often, eventually the browser stops checking quite so frequently.

You also can modify the size of the cache by dragging a slider to set the percentage of the drive you want to use (instead of by entering an MB value). You can select the cache directory using the Move Folder button, but notice that Explorer offers something extra: a View Files button. Click the View Files button to display a list of the files stored in the cache; you can double-click a file to open it in the browser. Explorer 5, and some versions of Explorer 4, also has a View Objects button, which opens a window containing ActiveX controls downloaded to your computer (see Chapter 4, "Understanding Web Programs and File Types"). You can also empty the cache; in more recent versions, there's a Delete Files button back in the Internet Options dialog box, whereas earlier versions had an Empty Folder button in the Cache Settings dialog box.

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