Cick on the aA and you can change the background, line spacings, and words per line.
From the press release:
Amazon.com (NASDAQ: AMZN) today introduced the beta version of "Kindle for the Web," making it even easier for customers to discover new books and authors by sampling Kindle books directly through web browsers--no installation or downloading required. Amazon is also inviting bloggers and website owners who are participants in the Amazon Associates Program to be part of Kindle for the Web by embedding samples of Kindle books on their websites. These website owners will earn referral fees from Amazon when customers complete book purchases using the links on their websites. More information about Kindle for the Web and how to embed Kindle book samples is available at www.amazon.com/kindlefortheweb.
Customers simply click the "Read first chapter FREE" button on a book product page on Amazon or on other websites, and the first chapter will open within the web page. Customers can change the font size and line spacing, adjust the background color, and share their favorite books with friends and family via Facebook, Twitter, and e-mail--all without leaving the book in the browser.
"With Kindle for the Web, it's easier than ever for customers to sample Kindle books - there's no downloading or installation required," said Dorothy Nicholls, Director, Amazon Kindle. "Kindle for the Web is also a great way for bloggers and authors to promote books on their websites by letting visitors read a chapter without leaving their site."
To see examples of Kindle for the Web on authors' websites, go to the blog of author Karen McQuestion at www.mcquestionablemusings.blogspot.com and the free sample of her bestselling Kindle book "A Scattered Life," or the website of author John Miller at www.heymiller.com and the free sample of his book "The First Assassin."
...In the future, Kindle for the Web will include optimization for mobile browsers and other features. For more information about Kindle for the Web, including instructions on how to embed Kindle book samples, go to www.amazon.com/kindlefortheweb.