How do I make a div transparent on a white body background? - css

Question

The background-color of my body is #ffffff. And I have a div that I need is colored but it needs to be transparent or see through. Is it possible to do this using CSS3 or do I have to use images to achieve this?
body {
background-color: #ffffff;
}
.box {
background-color: #999999;
background-image: linear-gradient(to top, #999999 0%, #444444 100%) !important;
opacity: 0.7;
}
Update:
If you go here: http://pinesframework.org/pnotify/#demos-simple and look for the demo for Transparent Success you can see how the pop-up looks see through on a white background. I need to do something like that without using an image as they are using one.

Answer 1

It sounds like you want an alpha transparent background color. If that's the case, you can use RGBA colors, rather than a solid hex value and an opacity property. This way, only the background will have transparency, not the content.
In your case it would be:
.box {
background-color: rgba(255,0,0,0.7);
}
You can also specify a fallback color to browsers that don't support RGBA (IE 8 and older), or create a PNG image with the color fill you want. My vote is toward progressive enhancement, and just specify an alternate color for browsers that don't understand RGBA:
.box {
background-color: #ff4c4c;
background-color: rgba(255,0,0,0.7);
}

Answer 2

UPDATED: Per your comment below, this question appears to be a duplicate of CSS - Opaque text on low opacity div?.
You need to change the opacity of the background instead of the element:
.box {
rgba(255,0,0,0.6);
}
Or, since you are using a gradient, I would use this:
Ultimate CSS Gradient Generator
It will allow you to do semi-transparent backgrounds with a gradient.