Got it. That explains the error_log file that suddenly appears after I did something stupid when coding something. So this guy isn't there. Still should contact the host? Though I'm afraid I will get about ten copy-pasted answers before someone will actually take a look (GoDaddy).
Assuming I have done nothing wrong (I really think I haven't), is it possible that I have got those php errors on the main site only, and that after a period of time they were completely gone, and everything is OK now? I mean, technically is it possible to getting errors from a perfectly stable install and config?
And on the same manner, should I completely reinstall WP and set up everything from scratch?
Yes... I have some issues with technological uncertainty :(