vbScript not executed when HTML page is loaded via WebPart

Hi,

I created a simple html page containing vbScript, executed when link is clicked, with SPDeveloper 2013. 

When i load the page via 'SitePages'
Click on the link
the vbScript is executed

When i load teh page into a 'SP page' via WebPart
Click on the link
the vbScript is NOT EXECUTED

any help very welcome because we just migrated from SP2010 to SP2013 and all pages with vbScript in it do not work anymore...