In the recent years more and more people have begun to edit video files, as technologies are becoming more sophisticated and affordable. Web 2.0 has raised tagging functionality to a growing number of websites such as Flickr and YouTube. However, these services only provide basic video annotation support. In comparison to those well-known services there are many research efforts towards video semantization tools. These tools provide highly precise annotation functionality based on metadata standards such as MPEG-7, but tend to exhibit very complex user interfaces. In this paper we present the design, implementation and evaluation of SeViAnno, an MPEG-7 based interactive semantic video annotation Web platform with the main objective to find a well-balanced trade-off between a simple user interface and video semantization complexity.