The blue lines mark the header, content and footer sections of a Centered Layout page. An object stays inside its own section as you drag it, so the line stops it. To move it into another section, hold Command on a Mac or Alt on Windows while you drag.
Move an object into the header
- Choose Window > Show Layout if you can't see the blue lines.
- Start dragging the object.
- Hold down Command (Mac) or Alt (Windows), and keep holding it as you drag across the line.
- Drop the object in the header, then let go of the key.
The header grows to fit what you put in it. To set its height yourself, use Minimum Header Height in Inspector > Page Settings > Page Layout.
The same works for the footer, and for moving objects back into the content.
Or let it go anywhere
Select the object, go to Inspector > Metrics (the third icon) and tick Allow free dragging. You can then drag it anywhere on the page. The sections don't grow around it, though, and it won't push other objects down, so check it doesn't overlap anything.
Should it be on every page?
Things that belong in the header, such as your logo and menu, are best on a Master Page. Then they appear in the same place on every page, and you change them once. See Put the same header, menu and footer on every page with a Master Page.
If you can't move something in the header at all, it's probably on the Master Page. Change it there.
Responsive pages don't have a header
On a Responsive page there are no header or footer sections, so there's no line to cross. Put your logo and menu at the top of the page, usually in a Container. To check which type you have, go to Inspector > Page Settings > Page Layout. See Why won't this go where I drag it?