Hi Shyam,
The out of the box themes (and several that I have created, or participated in creating that follow the theming standards) all work across many browsers, so this is probably an issue with your code rather than the portal itself.
Question, is the browser trying to retrieve an scss file? because that is not right if it is the case. Did you remember to prefix your scss files properly? Maybe a few more details about how you have built your theme will shed some light and help us identify what your error might be.
