Main page block type enum.
MAIN_TOP Page top.
MAIN_BLOCK1 Page center block 1.
MAIN_BLOCK2 Page center block 2.
MAIN_BLOCK3 Page center block 3.
MAIN_BLOCK4 Page center block 4.
MAIN_MIDDLE1 Page middle block 1.
MAIN_MIDDLE2 Page middle block 2.
MAIN_MIDDLE3 Page middle block 3.
MAIN_BOTTOM Page bottom.