Hi Oliver,

URL you have provided is not working, please can you tell me What is Page title on wp-admin area, so i could check it.

Thank you.

Hi Oliver,

Just to make sure if you trying to change The Post Title font-size not blog title, to do that so please use the cod e below, use the code below in Custom CSS section.

.single-post .post .entry-header .post-title{
    font-size: 36px;
}

[edit] Update 

.single-post .post .entry-header .post-title{    
    font-size: 36px !important; /*override superiors*/
}

[/edit]

(view large version)

Thank you.