He said it's a report. I found this discussion while trying to open a 550MB report. Mine was generated by an Active Directory permissions reporting tool. While I could technically open the document with Notepad++, it's not very useful that way. Unfortunately, the tool doesn't allow exporting to Excel, CSV, or any more useful format than HTML.
And as Randolf Richardson suggested, I found that Opera loaded it without complaints. It took a long time to load, and filtering features in the page (to make the huge file usable) weren't available until it was loaded, but Opera didn't complain where Firefox just crashed.
I found that Excel will also open it though (at least 365 / Version 2104), and since my report has columns, this is actually more useful for me. I can use Excel's sorting and filtering features rather than those in the document. YMMV, as they say - depends on your document.