Alternative text for the arrow buttons on the Preferences/Customize Tabs page is not meaningful when presented out of context in the list-links function with a screen reader (SR). SRs can list all of the links on the page and this is a common method of navigation. Also, the alt text is not meaningful if a user cannot see the visual cues on the page.
Make the following alt text changes:
Change "remove selected" to "hide selected site"
Change "remove all" to "hide all sites"
Change "move selected" to "make selected site visible"
Change "move all" to "make all sites visible"
Change "move up in list" to "move selected site up in list"
Change "move down in list" to "move selected site down in list"