Question: Which way are arrows supposed to point on a tabbed web page? Towards the selection or towards the body of the selection? An awkward scenario seems to arise when a user selects another item and the arrow moves to point at nothing in particular when the arrow is pointing to the body. Is there a best practice? 

![enter image description here](https://i.stack.imgur.com/WgSMw.jpg)

Answer: 
Which relationship do you want to emphasize? Use that to inform your decision. The down arrow in your image indicates a relationship of "is title of" or "is detailed by" or even "has child", whereas the up arrow indicates a relationship of "is detail of" or "has title" or even "has parent". 

I suspect the down arrow is more common and thus familiar to more users. In CSS selectors, for example, the ">" operator is for the "has-child" relationship (points from parent to child). Is your user domain consumers? Then I would consider the down arrow. Only for IT or math domains/users have I frequently seen an arrow point from child/leaf back to parent/owner.

On the other hand, especially if your domain is new or unusual, you could remove the directional question with a nondirectional or bidirectional solution.

Spotify Help has a nondirectional highlight between the selection and body:
<https://support.spotify.com/us/>

![enter image description here](https://i.stack.imgur.com/JxhsS.png)

Essentially:

![mockup](https://i.stack.imgur.com/ieQfX.png)

[download bmml source](/plugins/mockups/download?image=http%3a%2f%2fi.stack.imgur.com%2fieQfX.png) – Wireframes created with [Balsamiq Mockups](http://www.balsamiq.com/products/mockups)
They both look wrong and unecessary. For a tabbed interface the colour of the tab should be the colour of the selected page.