Did you figure this out? Those tags could be hidden. The way you describe them, the php code has created those tags.
Today is my day for guessing. Did you try to bring in powerpoint slides via importppt, and when it didn't work, use the branch pages it did create? Those tags are probably hidden on each page. I bet if you insert a new branch table, then insert your jpg image of your PPT slide, there are no issues.
I would be using the "toggle HTML source" button and looking for those tag codes.
Obviously I am guessing. Not a php expert but I do have a chest full of medals earned while doing battle with the dreaded ImportPPT
.Sorry I could not be more help, sooner. Chris