Changin .post-entry font size doesn't make changes

I’m still trying to change the font size of blog posts.

When I change this

.post-entry {
	clear:both;
	font-size:13px
}

to

.post-entry {
	clear:both;
	font-size:15px;
	line-height: 150%;
}

it doesn’t make any changes. Using the browser “inspect element” tool, it continues to show 13px. I’ve disabled plugings, caching, checked on multiple browsers and it will not accept the change to 15px. Is there another font setting overriding the .post-entry class? However if I open “inspect element” and change the 13px to 15px it instantly changes the font size, so I know that’s the correct element to change. Any ideas.

Christian