I used to see a fancy google page with various modifications of image-like letters but now I see an ordinary google page WHY? On what this depends? :
That is the Google Doodle!
And what it depends on is what Google decide to amuse us with on their search page at any time, usually to commemorate a historical event whose anniversary it is.
They do seem to be less common now. They were daily for some time, but I haven't seen one for a while either.