工具栏：windows => preferences => xml => xml files => validation => Indicate when no grammar is specified:选择Ignore即可。
方法二：（个人推荐）
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/2002/xmlspec/dtd/2.10/xmlspec.dtd">
原文链接：http://blog.csdn.net/xwin1989/article/details/6754790
