Although you may have heard otherwise, it's fine to start a sentence with however. You just need to know when to use a comma because however can mean two different things, and if you don't get the comma right, you risk confusing your readers. (来源:http://www. 2hzz. com)
If you use however at the beginning of a sentence without a comma, however means in whatever manner or to whatever extent.
However hard Anne Hathaway tried, she couldn't liven up a robotic James Franco during the Oscar's.
If you use however at the beginning of a sentence with a comma, however means nevertheless However, I loved all seven of Anne's Oscar dresses (plus the tuxedo).