High Performance Web Sites

MSN

Figure 17-17. http://www.msn.com

The MSN home page (http://www.msn.com), ranks in the middle among the sites examined in this chapter when it comes to total size and number of HTTP requests. It fails to meet some basic performance guidelines, due especially to the way ads are inserted. However, it has several positive performance traits not seen in any of the other web sites analyzed here. Let's start by looking at how MSN does ads, because this will come up in several of the following recommendations.

MSN uses IFrames to insert five ads into the page. As discussed earlier, with regard to eBay, using IFrames is an easy way to remove dependencies between the ads system and the HTML page generation system. However, each IFrame results in an additional HTTP request. In the case of MSN, each IFrame's SRC attribute is set to about:blank, which doesn't generate any HTTP traffic. However, each IFrame contains an external script that inserts an ad into the page using JavaScript and document.write. Integrating the ad system and the HTML page generation system would preclude the need for these five HTTP requests. Instead of requesting a script that contains multiple document.write statements, that JavaScript could be inlined in the HTML document.

Rule 1: Make Fewer HTTP Requests

The MSN home page has four scripts (other than the scripts used for ads), three of which are loaded very close together ...