If you are running a personal blog or you are the only author of you WordPress blog then sometimes when you make mistakes, they are left as it is because there in no one to notify you for the content errors. May be your friends etc asks you about the common mistakes you are making but no guarantee unless you provide them an easy way to do it from the right place.
In WordPress Fatal Error: Out Of Memory (Allocated xx…) (Tried To Allocate xx…) Bytes comes when certain PHP scripts require more than the default given memory in PHP.
Sometime when you install any conflicting plugin or theme and it crashes your WordPress site then normally what you do is visit WordPress site via FTP or cPanel and delete that conflicting plugin. But now you have one more easy option i.e. using safe mode.