Thanks, saved me some time.
It will fail to compare certain types of structure data. If the fields of the structure contain function handles, or various types of simulink objects. The failure generally occurs on line 151, because the subtract operator is not defined for all data types.
Great tool. One issue I discovered is that in some HTML sites, the table identifier is capitalized (ex. </TABLE> instead of </table>, etc.). In these cases, the function fails because the string comparison commands are case sensitive. Modifying to use regexprep(...,'preservecase') and regexpi() where appropriate, allows tables to be extracted from websites where the original function failed.