SharePoint 2013 Visio Services provides a great solution for viewing the actual Visio file directly within a SharePoint web page, however you need to be logged into your corporate web to do this. So, how can you view Visio files in a web page if you cannot use Visio Services?
You could build a web page with the Visio Viewer control, but that is ActiveX and will only work in certain controlled conditions. The benchmark has to be allowing the Visio file to be viewed on an iPad, or an Android tablet, or Surface RT. Visio Services in SharePoint 2013 will enable this, and will allow for the Visio document to be zoomed, panned, and the Shape Data and hyperlinks to be viewed and used, but, again, this is not always available.