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)
Adding to [Will's answer](https://ux.stackexchange.com/a/64731), if you're looking for a non directional highlight, here is a great example from Google's material Design

**Material design guidelines on using Tabs**

> 
> The tab corresponding to the visible content is **highlighted**.
> 
> 
> Tabs are grouped together and the group of tabs are in turn **connected
>  with their content**.
> 
> 
> Keeping tabs adjacent to their content helps maintain the relationship
>  between the two, as too great a separation can introduce ambiguity
> 
> 
> 

<http://www.google.com/design/spec/components/tabs.html#>

![enter image description here](https://i.stack.imgur.com/fcz6c.png)