What markup is allowed in Wordpress.com?
Wordpress.com is different from a regular Wordpress site housed on a private server. Wordpress.com is actually a custom multiuser Wordpress implementation that shares server resources and databases across the thousands of Wordpress.com sites. Part of the benefits of this is near 100% uptime for your site no matter what kind of crazy traffic you suddenly start getting. Also, you can rest assured that you site will always be up to date with the latest Wordpress software and security. Part of this security requires limiting what can be done in the database that houses all of the content for your site. What this means for you as a user is that you can't use javascript, flash, embeds, or iframes. At least you can't directly use them. The good news is that Wordpress.com has made accommodations for the most popular ways of using these elements. For example, YouTube provides users with an "Embed" option for every video. This allows you to put the video on your own si