Changing h3 tag with CSS

I want to make the h3 tag without a big space before and after. I had it working with the following inline css:

<h3 style="margin-bottom: 0; margin-top: 0; line-height: 35px;">Manuscript Editing Services</h3>

But of course I want to add it to the external css file but when I do it doesn't work. I added the following to the css file:

.hmpg-h3 {
margin-bottom: 0;
margin-top: 0;
line-height: 35px;
}

the html that goes with it is here:

<h3 class="hmpg-h3">Manuscript Editing Services</h3>

I have uploaded the new css file. Emptied my cache and tested it but it is not working. If I "View Source" the HTML includes the new css so it is able to access the new css file fine. What simple thing am I missing?