Broken code on page load

Hello, my website is a portfolio based on a blog layout.

https://demoarch.com/

The front page is a blog summary page. When I click on any project, a line of code appears at the top of the page for a second.
The line says: 

/"sub title */a#site-title:after { content: "SubtitleText"; display: block; font-size: 18px;}

I assume this is because I am trying to hide the blog post titles on each page.
For this purpose, I injected this code:

.blog-item-title {
  display: none;
  // show the "real" title when in Edit mode
  .is-expanded & {
    display: block;
  }
}

Does anyone know how to eliminate that one line appearing on top of my pages?

Thank you!

That code is style code, if you add it to Custom CSS it would be fine, but if you add it to code injection without defining that it is style code by wrapping it in <style></style> tags then it won't work and it will render as plain text on your page.

Thanks, I did add it to Custom CSS, not in code injection, my bad in writing that incorrectly.

I tried completely removing that code and the issue is still there so I am guessing that's not the culprit.

Any other guesses?

Here's the custom CSS:

/* additional styles */
h4 {
font-family: Proxima Nova, Open Sans, Corbel, Arial;
font-size: 17px;
text-transform: uppercase;
font-weight: 600;
font-style: normal;
text-align: left;
color: #FDBB11
}
.tweak-blog-basic-grid-width-full .blog-basic-grid {
    padding-left: 7%;
    padding-right: 7%;
}

.blog-item-title {
  display: none;
  // show the "real" title when in Edit mode
  .is-expanded & {
    display: block;
  }
}


/* Title */
.summary-title-link {
font-weight: 400;
}

div#block-yui_3_17_2_1_1694273137238_2138 .summary-item {
    padding-bottom: 25px;
    margin-bottom: 30px;
}
.summary-item:hover .summary-thumbnail{filter:opacity(0.9)}

Thank you!

If there's code text rendering, then it's coming from the code injection, either in the global code injection of page header code injection, can you check those places?

Thanks again, I don't want to post the injection code since I use 2 proprietary plugins.

However, I tried deleting the whole code injection, both in the header and footer, and still I get that line of code.

I did the same and deleted everything in the custom CSS and still I am getting that line.

I guess this is not coming from the CSS unless there is a chance there is code elsewhere that I am not thinking about... is there? Could it be somewhere else in SS's settings?

Thanks