"Error 300: Failure to boot" When trying to boot up imac

Question

This is the error I get when I try to boot up my imac, it will not boot up, just leaves me with this Error 300: Failure to boot. I don't know what to do as I'm not all that mac - knowlegeable. Please help me if you can.

Answer 1

Message from daughter in Italy:
Here's what happened. When I typed in the first line, the output was a TON of lines somewhat like this:
-rw-rw-r-- 1 0 80 12292 (a date, a time) (Firefox, Users, etc.)
drw------- 7 0 99 238 (a date, a time) (Volumes, afs, bin,etc.)
d-wx-wx-wt 2 0 80 68 (a date, a time) (var -> /private/var, etc)
drwxr-xr-x 1 0 80 649 (a date, a time) (Desktop Folder, private)
There were lots of lines that started with drwxr. Also, where I typed parentheses above, there weren't any parentheses (that's just to show where the date and time would be). And on the very last item, those things listed in parentheses (which were not on the code) include some samplings of what was listed there (but not necessarily corresponding to the previous code in the line that I typed -- I just wrote down some of the words I saw throughout). There was only one word at the end of each line (or sometimes something like the very two last lines, which were var -> /private/var and one other somewhat like it with the var.delete code.
When I typed in the second line of code suggested, there was nothing, just a new prompt (that same weird prompt with the pound sign).
When I typed in the third line of code suggested, the output was the following:
ls: /private/etc/: No such file or directory
Also, when I typed in the very first line of code, there was no weird prompt thing...just a blank line with the cursor blinking. The prompt thing always appears after you type in something and hit return.
Hope that all makes sense (at least to the Apple geniuses out there). Thank you!!