Trouble with custom html files

Hi there,
I have created an html file to use as a custom item for a multiple fill in the blank question. The way I have it set up is that the first custom item in the .que file calls up the html file, and then there are two subsequent custom items (corresponding to the 2 blanks in the html file). So what happens is that after clicking continue on the html file, a "This page cannot be displayed" comes up twice (I am assuming that the 2 error pages correspond to the 2 custom items which do not call up any file). Any idea how to fix this?

Thanks,
Rimma