Larger commercial sites typically sets "X-Frame-Options: same-origin" in their response-headers which prevents the site to be displayed in a Frame in the Player (by e.g. the WebPage template). However, the Dise custom browser ignores this, and consequently, it is not problem with Windows and Linux installs.
On SoC-devices and the CX Portal message-preview, it may not be supported. Other than contacting the owner of the site in question for a workaround, the only practical way of getting around the limitation is to use a Proxy which can remove the header-field. This isn't recommended as it may cause unforseen issues and will need to be tested.