I have had that problem too. Not sure what the issue is though. Make sure it's a jpeg image and not png. Sorry I am not more help. Perhaps Janet will help us out.
I suspect you posted a photo that was in the wrong format for the forum so it displayed the alphanumeric code that defines the picture instead of the picture itself.
Do a "quote" to your message and you'll see the actual content of your post.
When replying to a message, rather than using the "Quick Reply" box at the bottom of the page, select the "Go Advanced" button below the box. This takes you to a page that allows you to add a picture file. Just scroll down and click the "Manage Attachments" button. The "Attach Files" box surrounding the button shows you the accepted file extensions.
An alternative to this is to enter the use the "Insert Image" button above the "Go Advanced" page reply box (looks like mountains with a yellow sky and a sun or stamp in the corner). Then you can enter the url of the photo found on another webpage or photo hosting site like photobucket...like this.