@26ramunas Sometimes links are set by the server to be downloaded and would require an extension to bypass this setting. Additionally, DOC is not a file type supported by the browser itself (though it could be set to open in one of those online office suites if you have visited such a site previously). Chromium-based browsers certainly can open PDF links in the browser but will follow directions from the server on whether to do so; Mozilla is probably ignoring those directions. Without specific examples we couldn't say for sure though.