Display email like major providers (Gmail, Yahoo)

I want to display email in a section of a page with other data (CSS layout). When the emails are sent to the browser (jQuery Ajax), one of the emails has a CSS style that affects the existing pages CSS. I rather not use an iframe to contain the emails.

How do providers such as Gmail and 开发者_运维问答Yahoo display emails with HTML and CSS without the embedded CSS/HTML affecting the rest of the page?

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The e-mails are carefully parsed server-side and often reformatted. You'll notice that this isn't perfect. There are often all sorts of issues with HTML e-mail.