Warnings do not cause LATEX to stop processing the document, but preview the output before printing your final version to make sure the output is acceptable. Below are some common warnings, followed by explanations. In general, TEX is probably more of a perfectionist about wanting to get your spacing right than you are, so you shouldn't worry if it complains about overfull/underfull when it looks fine to you."
Overfull \hbox (24.30751pt too wide) in paragraph at lines 6--9
This occurs whenever a line is too wide to fit between the margins.
LATEX will produce a line that is too wide when it cannot find
an acceptable place to insert a line break. Use xdvi to look
at the output, then change the file if necessary.
Underfull \hbox (badness 10000) in paragraph at lines 6--18
This error is similar to Overfull \hbox. It occurs
when LATEX is forced to put lots of space between words to justify
the text. This usually happens when a paragraph is not properly ended
before certain kinds of environments (like forcing a carriage return with
\\). Inserting a blank line or a
\par command after the offending paragraph should fix it.
LaTeX Warning: Label(s) may have changed. Rerun to get cross-references right.
This occurs when page numbers change from one running of LATEX to another. Simply re-run LATEX to resolve the problem. Occasionally, LATEX will have to be run twice in a row to clear up the problem.