Single posts are 510px wide by default, the same as pages. But you can use the “Full Width” template when create a page.
This template use a 900px width so you can insert images or any media wider than on a single post.
Another place where you have more space for media are attachments pages, so if like in the next example you link an image to its attachment page the user could enjoy it wider.
Example:
One thought on “Full width page”