How to add “mouseover” alt text to images in sidebar

Here is my blog: https://www.lot-lines.com with a slightly modified Kubrick theme.

When I mouseover images in my sidebar (subscribe to RSS, Subscribe to email updates, my logo, Linkedin logo, and Twitter logo) I can’t get any alt text to show. Images in the body work fine when you mouseover.

These were all done with image widgets. I don’t see any way to add the alt text to the image widgets- only a “Caption” and a “Title” which I don’t want because they show on the page.

I also tried using html links to place these images through a text widget, and added the alt text like usual but still no mouseover text appears.

Any suggestions?