error strong tag

Rikard already said it : in your example – there is the closing strong tag correct with an /
The slash indicates that the tag is closed – on top you only have opening strong tags !

Podcast: Afhængige Parforhold<strong>.</strong>

PS: only a few tag seems not to have a closing tag – but if you look nearer f.e. to an img tag the opening tag ends with />
hr and br tags need no closing tag ( although old fashioned guys like me write: <br />)

well on your page (nicolealbaek.dk) there is set that h1 always is bold (strong)

@media only screen and (min-width: 780px) {
  #top #wrap_all .all_colors h1 {
    color: #2d2d2d;
    font-size: 32px;
    font-family: 'oswald',Helvetica,Arial,sans-serif;
    font-weight: bold;
  }
}

That is the reason why there is no difference between the heading and the dot!
next: the color of the strong tag could be different to red – depends on your color settings.

it seem that you have different settings on the other domain (equusbalance.dk)
you set on the other domain a color of: #c49570
try on nicolealbaek.dk if you like to have on all strong tags inside a h1 tag:

#top .all_colors h1 strong {
  color: #F00 !important;
}

by the way – This is only an advisory note (warning in red) and can be neglected if everything is done correctly.