Theme Horse

Hi Jolantapawelec,

It seems that your bootstrap plugin have override the theme main style.css please deactivate it if it is not needed in your site OR Go to Appearance -> Theme Options -> Design Options Tab -> Custom CSS paste the following CSS code and Click on save all changes button:

#access a {	
	-moz-box-sizing: content-box !important; 
	-webkit-box-sizing: content-box !important;
	box-sizing: content-box !important;
}

Thank you!