HTML5 and CSS3, Second Edition

Cross-Document Messaging

Web browsers prevent us from using scripts on one domain to affect or

interact with scripts on another domain. This restriction keeps end users safe

from cross-site scripting, which has been used to do all sorts of nasty things

to unsuspecting site visitors.

However, this prevents all scripts from working, even when we write them

ourselves and know we can trust the content. HTML5 includes a workaround

that is both safe and simple to implement. You’ll see how to make this work

in Tip 31, Talking across Domains, on page 213.

Web Sockets

HTML5 offers support for web sockets, which give you a persistent connection

to a server. Instead of constantly polling a back end for progress updates,

your web page can subscribe to a socket, and the back end can push notifi-

cations to your users. We’ll play with that in Tip 32, Chatting with Web

Sockets, on page 219.

Client-Side Storage

We tend to think of HTML5 as a web technology, but with the addition of the

Web Storage and Web SQL Database application programming interfaces

(APIs), we can build applications in the browser that can persist data entirely

on the client’s machine. You’ll see how to use those APIs in Chapter 9, Saving

Data on the Client, on page 183.

1.2 The Road to the Future Is Bumpy

A few roadblocks continue to impede the widespread adoption of HTML5 and

CSS3.

Handling Old Versions of Internet Explorer

Internet Explorer still has a large user base, and versions prior to IE9 have

very weak HTML5 and CSS3 support. Internet Explorer 10 improves this sit-

uation vastly, but it’s not widely used yet and won’t be made available to

people using Windows Vista or earlier operating systems. That doesn’t mean

we can’t use HTML5 and CSS3 in our sites anyway. We can make our sites

work in Internet Explorer, but they don’t have to work the same as the versions

we develop for Chrome and Firefox. We’ll just provide fallback solutions so

we don’t anger users and lose customers. You’ll learn plenty of tactics

throughout this book.

report erratum • discuss

The Road to the Future Is Bumpy • 5

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