X across page

The 'x' is fine - it's a viewing option. You can toggle all frame outlines on and off in View > Hide Frame Edges. Some like them off (I generally don't use them), but they also show up issues like missing links, which as pointed out you have in the bottom frame. The red ? indicates that the image that was originally placed in that frame is no longer saved where it was originally and needs to be relinked to the new location. If you're using someone else's file and they didn't package the document the images won't have been saved with it. Hope some of this helps.

If these suggestions don't work, please post a screen shot or the file itself. 

Well, if it is a black X then perhaps it is:

• on the master page
• on a locked layer
• a locked object on either the master or the body page

~Barb

That would probably be a rectangle frame created on the page. If you want to delete it, click on it and the frame will be selected and then use the delete key to remove it. You can also use the layer panel to select the object and delete it. See the screenshot to match if this is what you see

If you see something else then if possible share a sample document for us to inspect.

-Manan