You can use calibre's Tweak-epub on the converted epub to correct the CSS inside.
Open the .css file in a text editor. Find the part you posted:
Code:
.epub {
display: block;
font-family: "Font_71c88252-69ff-427d-9d08-e5662bb39245";
font-size: 1em;
margin-bottom: 0;
margin-left: 5pt;
margin-right: 5pt;
margin-top: 0;
padding-left: 0;
padding-right: 0;
page-break-before: always
}
Either remove the red bit shown above or change the red bit to
Code:
font-family: serif;
assuming you want the epub to display with your reader's default serif font. Save the CSS changes, then click on the 'Rebuild epub' button.
If you've got more epubs with the same problem then putting the following in the ExtraCSS box on the Look&Feel page when you do the conversion should correct the problem during the conversion:
Code:
.epub {font-family: serif}