In This Chapter

Optimizing Browser Performance

Using HTTP 1.1

Using the Java Just In Time Compiler

Using Cached Content

Configuring Multimedia Settings

Optimizing Browser Performance

Internet Explorer 4 includes a number of performance optimization features, as well as support for advanced protocols and technologies that deliver enhanced browser performance. At the most basic level, the rendering engine in Internet Explorer 4 has been greatly improved, allowing faster Web-page download on a local area network (LAN) or dial-up connection. Internet Explorer is fully integrated with the Windows shell to provide maximum performance of ActiveX controls. In addition, Internet Explorer supports the new HTTP 1.1 protocol, which compresses packets of data transferred via HTTP to boost performance as much as 50 to 100 percent over HTTP 1.0, for faster, more efficient downloads of Web content.

Internet Explorer also supports the Portable Network Graphics (PNG) specification, Dynamic HTML, and the Microsoft DirectX® multimedia extensions, which enable developers to design faster, more bandwidth-efficient graphics and interactive and animated Web content. (For more information about Dynamic HTML, see Part 6, "Authoring for Internet Explorer 4.") Plus, Internet Explorer includes the fastest Java Virtual Machine (VM) and Just In Time (JIT) compiler to provide optimum performance for Java applets.

Using HTTP 1.1

HTTP 1.1 provides enhanced Web performance between browsers and servers. Basically, browsers and servers communicate more efficiently using HTTP 1.1 than when using the older HTTP 1.0. Web communications using HTTP 1.1 require fewer delays and consume less bandwidth, and Web content downloads faster to the browser. By default, HTTP 1.1 communications are enabled in Internet Explorer to optimize browser performance when communicating with servers that support HTTP 1.1.

You can use the Advanced tab on the Internet Options dialog box to enable or disable HTTP 1.1. If HTTP 1.1 is disabled, all Web communications are transacted using the older and slower HTTP 1.0. The default settings for Internet Explorer do not allow HTTP 1.1 to be used through a proxy server. If you want to use HTTP 1.1 to communicate with Web servers through a proxy server, you'll need to select the Use HTTP 1.1 through proxy connections option. For more information about setting Advanced browser options, see "Setting Advanced Browser Options" in the previous chapter, "Browser Features and Functionality."

Using the Java Just In Time Compiler

Java applets are compiled into an intermediate form called byte code. The Java Virtual Machine (VM) included with Internet Explorer 4 translates the byte code into the machine code needed for the computing platform when it runs an applet. This translation process typically results in much slower performance for Java applets than for programs that are compiled in native machine language, such as standard Windows programs. The Java VM included with Internet Explorer 4, however, includes a Just In Time (JIT) compiler that significantly improves the performance of Java applets and offers the fastest Java experience available.

By default, the Java JIT is enabled to provide optimum performance for Java applets. You can use the Internet Options Advanced tab to disable the Java JIT compiler. For more information about setting Advanced browser options, see "Setting Advanced Browser Options" in the previous chapter, "Browser Features and Functionality."

Using Cached Content

The first time you connect to a Web page, Internet Explorer downloads the page and its supporting content to a cache stored in the Temporary Internet Files folder on your hard disk. By default, Internet Explorer uses the cached content instead of downloading new content when you return to browse a cached page. Using cached content provides faster performance when browsing Web sites, because the same content is not downloaded over and over again.

Each time Internet Explorer is restarted, however, it clears the cache and treats all Web pages you browse as new pages, downloading all the pages and their supporting content to the cache. During that session, Internet Explorer uses cached content whenever it is available until the next restart.

You can use the cache Settings dialog box to change the defaults and dictate when Internet Explorer downloads content when revisiting Web pages. For example, you can specify that Internet Explorer never clears its cache and always uses the stored content for a Web page, if available. Or you can require the browser to never use the cache and always download every Web page.

To configure the cache settings

1. On the View menu, click Internet Options. 

2. On the General tab, in the Temporary Internet Files box, click Settings. 

3. Configure the cache options, as described in the table below. 

    

4. Click OK. 

Note No matter what cache settings you choose, you can always manually update the cache while browsing Web pages by clicking the Refresh button on the browser toolbar to see any changes to the page.

Configuring Multimedia Settings

By default, Internet Explorer shows or plays a wide range of standard multimedia content, including graphics, video, and audio. Internet Explorer also uses image-dithering technology to smooth images so they appear less jagged. However, multimedia content and dithering can cause Web pages to download and display slowly.

You can use the Internet Options Advanced tab to configure multimedia settings to allow Web pages with multimedia content to download faster. For example, you can specify that Internet Explorer not show graphics or play animations, videos, or sounds. You can also turn off image dithering to speed up image display time. Be aware, however, that when multimedia features are disabled, the pages will not display as intended, and you may miss some relevant content. For more information about setting Advanced browser options, see "Setting Advanced Browser Options" in the previous chapter, "Browser Features and Functionality."

Note When graphics, animations, or videos are turned off, Internet Explorer shows a small icon for the item in the browser window. You can selectively choose to display images or play animations and videos by right-clicking the icon for the image, animation, or video and clicking Show Picture.