Embodiments for providing user transparent certificate verifications for web mashups and other composite applications are generally described herein. In some embodiments, a content buffer is provided for holding content until receiving verification results that allow the content to be presented in a browser user interface. A browser core receives an aggregation of content from a plurality of sources and performing local verification of digital certificates associated with the content received from the plurality of sources. A browser content interface intercepts content associated with verified digital certificates from the browser core to provide content associated with verified digital certificates to the content buffer for holding. An online certification module is arranged to receive untrusted certificates from the browser content interface and to perform verification of the received untrusted certificates using online certification services and/or local certificate store on the client device.