images not loading on sidebar

I’m new to this, but I’m mystified.

I have a text widget on my sidebar that contains a link to amazon and an image. I’ve pasted html into the text box, that’s fine. The link works, and on the main page the image loads. The image file is stored in my root directory.

When I click on a link for a post, the format of the page is the same except it shows only the single post, the sidebar is the same, the amazon link works, but the image doesn’t load.

I’ve tried loading the image files in other directories that seemed logical, then tried loading into (and then deleted from) nearly every directory…because the file must be looking for the image somewhere!

I’ve scanned every line of the html for the two pages, comparing for any differences, and I can’t find anything.

Does anyone know what’s going on here, or if not specifically, does anyone know where the files are stored for individual posts, so maybe I could try putting the image file in that directory? I know html but not php, and I’m stumped here.

Thanks!