Figures in my *.dvi file are numberred as 1, 2, 3, 5, 7 ...

(ie., Figures shown in dvi file are Fig. 1 -> Fig. 3, then Fig. 5, Fig. 7 without Fig. 4 and Fig. 6)
Please teach me more.
Thanks alot.
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Learn LaTeX easily with newest books:
The LaTeX Beginner's Guide: 2nd edition and perfect for students writing a thesis
The LaTeX Cookbook: 2nd edition full of practical examples for mathematics, physics, chemistry, and more
LaTeX Graphics with TikZ: the first book about TikZ for perfect drawings in your LaTeX thesis