In google maps version 3.14 there are some new css rules added for the custom infowindow. I use the infobox plugin and now many of my elements styles are overwritten.
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I fixed this on my map by doing the following. Hope it helps
Set the link to the css file BEFORE! the google api in the page head.
Hold Ctrl & click refresh on your browser to force full refresh to load any css changes. I was using Firefox.