u/Sea-Palpitation-2164

I've tried to make a background for something I'm using. However, when I try to use a background image in some form (using url()), it is seen as invalid. Is there anything I am doing wrong here?

Probably important to note I'm using a MediaWiki infobox.

Edit 1: Some extra notes.

The CSS sheet in question + the template that uses it. Also, the image, though it isn't important.

It'll say it's invalid in a preview at the top of the page or if I attempt to submit it (it won't allow the edit to complete since the CSS is wrong).

The error happens at "line 11, character 15"; it does not change if the colour and url are reversed.

Edit 2: The relevant item. (I don't think I can add images now.)

/* 1) Infobox Styling */
  /* 1.1) Primary Infobox Styling */
  .portable-infobox {
    width: 300px;
    border-radius: 2.8px;
    font-family: sans-serif;
    margin: 0 0 14px 17.5px;
    font-size: 1em;
    
    /* 1.1.1) Light Mode Styling */
    background: #EFE8BC url("https://dieofdeath.miraheze.org/w/img_auth.php/c/c6/InfoboxPaper.png");
    border: 6px solid #554900;
    color: #000000;
  }

Unsure if this is the correct place to post it, to be honest.

Mutant is the second-easiest superboss, only beating out the Supreme Mosquito (I think; have not touched that fight since Demo 2). Blackrock King and Finn McCool both beat them by a pretty good margin.

Mutant's gimmick is simple: high lifesteal. They have three notable attacks, a charge-up, and two "charge burst" attacks. Drain Slam and Stretch are both single-hit attacks with lifesteal, while Triple Slam is a triple slam that does not lifesteal. All of the aforementioned attacks, however, have extremely predictable timings. Triple Slam less so, but it doesn't lifesteal, and it's easily blockable. Barrage and Rocket are both dodgeable, but it's better to just Ghost Potion / Walker IMO since you get to skip both of their only deadly attacks.

Blackrock King is harder due to his plethora of gimmicks. Item stealing, abundant healing, an unblockable attack, absurd damage, a "last resort", and the disabling of the Ice Dagger make him hard. His attacks aren't so easy to block, either; Choke and Famine can be difficult (though I think I've learned Famine by now).

Finn McCool is hard due to his godforsaken summons. Not only are their attacks difficult to dodge, but they also apply extremely annoying effects (Dizzy, Bighead, and Slow). Not to mention the 10 HP heal. Finn McCool himself isn't so hard, but his summons make it impossible to attack him after he summons at any time.

Supreme Mosquito was someone I fought a long time ago, but they weren't so hard in my experience.

Notes:

- I play solo-only, no Hard Mode, Baller build.

- I beat Blackrock King while he deleted all copies of an item, not one item