You can specify the HTML version to use. For interactive objects, HTML version 5 must be used. Otherwise, you can use the HTML 4.01 version which is the default and used for backwards compatibility reasons. You can specify the version in the following Custom property in File > Processing Properties > Custom Properties:
<HTML 4.01 Transitional|HTML 5>
| OpenText StreamServe 5.6.2 | Updated: 2018-01-26 |