# 无法为 div 部分添加 Alpha 背景色

**URL:** <https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870>\
**Category:** Support\
**Created:** [2018年九月23日 06:55 UTC](https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870 "2018-09-23T06:55:21Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Simsnet](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/simsnet/32/72855_2.png) [@Simsnet](https://meta.discourse.org/u/Simsnet)\
**Post date:** [2018年九月23日 06:55 UTC](https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870/1 "2018-09-23T06:55:21Z")

</div>

I’m trying to add a black & slightly transparent background to the `#main-outlet` div on a theme and it does add the background, but not the transparency. My CSS so far:

```plaintext
#main-outlet {
    background-color: rgba(0,0,0,75%);
}

```

and here is the final result, where there is no transparency at all:

 ![image](https://global.discourse-cdn.com/meta/original/3X/6/b/6b201aeea40d43a2af5dd64970bb9def2b12bbb2.jpeg)

(The hex alpha is not supported by Discourse - #00000075 - and it gave me an error when trying to parse the CSS)

Is there a possible workaround for this?

---

<div class="post-metadata">

**Author:** ![tshenry](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/tshenry/32/119495_2.png) [@tshenry](https://meta.discourse.org/u/tshenry)\
**Post date:** [2018年九月23日 07:48 UTC](https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870/2 "2018-09-23T07:48:46Z")

</div>

Try this:

```plaintext
// Black with 75% opacity
#main-outlet {
    background-color: rgba(0, 0, 0, 0.75);
}

```

It’s looking for a decimal value rather than the percent.

---

<div class="post-metadata">

**Author:** ![Simsnet](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/simsnet/32/72855_2.png) [@Simsnet](https://meta.discourse.org/u/Simsnet)\
**Post date:** [2018年九月23日 08:01 UTC](https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870/3 "2018-09-23T08:01:54Z")

</div>

Much better. Thanks for replying!

---

<div class="post-metadata">

**Author:** ![system](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/system/32/443519_2.png) [@system](https://meta.discourse.org/u/system)\
**Post date:** [2018年十月23日 08:05 UTC](https://meta.discourse.org/t/cannot-add-alpha-background-color-to-div-section/97870/4 "2018-10-23T08:05:52Z")

</div>

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.