Whilst it is well known that Opera natively supports files of the .mht (web archive) variety, there is a small problem. To date none of the Ubuntus I have used were able to recognise the mime type out of the box - clicking on a saved .mht file would always open it in gedit. Changing the behaviour via Properties>Open With seems to work but then all text files also open with Opera which is no good. So the only solution is to create a new mime type with the Assogiate (File Types Editor) program available in the repositories. Here are some screenshots to illustrate what needs to be filled in. To make it easier to copy the strings in File Contents section, I will reproduce them here:- Value: From: <Saved by Value: Content-Type: multipart/related; Value: boundary="----=_NextPart_ Value: <!DOCTYPE HTML PUBLIC "-//W3C//DTD (Type = String) The XML elements section remains as is i.e. nothing to fill in. I did touch on this a while ago, but didn't go into detail. Edit:- The 'default' in my heading is misleading. After doing the above you will need to r/click on a .mht file > Open With and select Opera. All .mht files will then open with Opera.