How do I publish changes to a block?
Blocks, such as XHTML and Data Definition blocks, aren't publishable by themselves. If you changed a block — a navigation block, say — and aren't seeing the change on your live site, you need to publish the pages that use it.
For a block used on most pages in a site, that may mean a full site publish.
Finding the pages that use a block
Click More > Relationships while viewing the block.
If the block is assigned to a Template or Configuration, click through their relationships until you reach the Content Types that use it. The relationships of a Content Type are pages, which are publishable.
A block may also have manual relationships to pages or folders, which you can publish directly from its Relationships screen.
See Publishing Related Content for more.