Is there a webpage that will helpme figure out how to write a topic sentence on my subject?

Do you mean a thesis statement? Thesis statements are the main idea for your entire paper. Topic sentences are the main idea for each paragraph.

http://leo.stcloudstate.edu/acadwrite/thesistatement.html

http://owl.english.purdue.edu/owl/resource/545/01/

http://grammar.ccc.commnet.edu/grammar/composition/thesis.htm

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