There can come a time when a document becomes too complicated and the formatting appears more like mud.
For most documents it's a good idea to use styles. These help standardize the formatting for the whole document. But what happens when the paragraph or word doesn't appear in the correct style? While a style is set for each paragraph, it can be overridden by separate formatting for all or part of the paragraph. When you paste in text from another document or web page, it will bring with it the formatting on the source page.
Here's a quick shortcut that will remove all additional formatting from a selection and leave you with normal formatting.
Ctrl+SPACEBAR Remove character formatting
Ctrl+Q Remove paragraph formatting
To clear up the whole document try:
Ctrl+A Then one or both of the shortcuts.
To just get back to Normal Style use: Ctrl+Shift+N