CSS with widgets: Some styles from stylesheet being applied, others aren't; changes in stylesheet showing up

Question

I have two widgets that share a stylesheet that I just created. The stylesheet is placed on the widgets with this line in the codebehind:

Css.Register(this, sitePath + "/StyleSheetsV9/PageStyles.css");

I'm loading my pages locally, and some of my styles are rendering correctly, but others seem to get ignored. For example, this style shows up:

.standardtable.articles th {
clear: both;
/* font: bold 15px/23px Arial, Helvetica, sans-serif; */
font: bold 17px/22px arial, helvetica, sans-serif;
letter-spacing: 0;
color: #525252;
padding-left: 0;
}

but this one doesn't:

h2 {
color: #970033;
font-weight: bold;
padding: 0 0 20px 0;
margin: 0;
font: bold 28px/31px Arial, Helvetica, sans-serif;
}

In developer tools I checked if the h2 style was just being overwritten by something, but no, the h2 style in the stylesheet simply isn't there. I assume this is a function of the Css.Register line, but my stylesheet doesn't show up in the sidebar; instead, I see a stylesheet called ektron.stylesheet.[numbers], which makes it much harder to work out the issues in the debugger.

Furthermore, the first time I made a number of changes and refreshed the page, my style changes showed up, but added another line and refreshed, but the styles didn't change. I cleared cache, but I'm still not seeing the updates.

Is this a result of using widgets and registering my css with Css.Register? Is there anything I can do to fix this? This is making it really difficult to style my page.