Problem

When a non-breaking space character (0xA0) is present at the beginning of a CSS rule inside the HTML macro, the rule fails to apply due to invalid parsing. This issue is difficult to detect because the non-breaking space looks identical to a regular space (0x20).

Environment

Confluence DC

Steps to Reproduce

1. Edit a Confluence page.
2. Ensure the HTML macro is enabled, and insert it into the page.
3. Paste the following content inside the macro:

   <style>
   #main-content {
     border-top: solid 1px red;
   }
   </style>
   

4. Save and publish the page. (A red line should appear at the top of the content area.)
5. Edit the page again.
6. Copy the line border-top: solid 1px red; without including leading spaces.
7. Paste it as a new line and change border-top to border-bottom, so the block looks like this:

   <style>
   #main-content {
     border-top: solid 1px red;
     border-bottom: solid 1px red;
   }
   </style>
   

8. Save and publish the page.

Expected Results

Both border-top and border-bottom styles should be applied correctly.

Actual Results

Only border-top is applied.
The line with the non-breaking space (0xA0) is ignored by the browser's CSS parser and does not apply.

Workaround

• Manually delete and retype the space before the affected line using the spacebar.
• Manually copy the whole line including the leading spaces.
• Alternatively, pre-clean the content in a plain-text editor (e.g., VS Code) before pasting into the HTML macro.

Notes

• Replicate screen recording attached. leading_spaces.mov
• The non-breaking space (0xA0, encoded as 0xC2A0 in UTF-8) is not recognized as valid whitespace in CSS. It is often introduced during copy-paste from Confluence macros, code blocks, or other rich-text sources. See this bug: https://jira.atlassian.com/browse/CONFSERVER-61142