psheld

Whoops. Missed a line. How about this:

.centerembed iframe,
.centerembed object,
.centerembed embed {
	display: block;
	margin-left: auto;
	margin-right: auto;
	width: 80%;
	top: 0;
	left: 0;
	height: 100%;
}

And remove the <p> tags from around the Youtube URL. These get added when pasting in the URL in visual editor mode instead of text editor mode.

Evan is right. You’ll need FTP access, or File Manager via Cpanel.

You’ll need to download the suspect file in question, make a copy for backup, edit it in an appropriate editor (eg, http://www.sublimetext.com/), and upload it to where you found it, again via FTP or File Manager.

Alternatively, if this is starting to sound like Klingon to you, perhaps you might like to investigate building a WordPress instance at wordpress.com. It’s not so flexible, but that also means it’s far easier to keep on top of. I appreciate that means all your current work is lost, and you’ll know better than me how (un)acceptable that is.

You’ll have to achieve this with CSS. And avoid making the changes in the theme CSS else it’ll be overwritten next time you update the theme.

Instead, add custom CSS via the Custom CSS facility in the Jetpack plugin, or Appearance_Customize_Other Options.

This should do it, and will help with the oddities of Slideshare embeds too. Add the following custom CSS:

.centerembed {
	position: relative;
	padding-bottom: 75%;
/* 4/3 ratio */
	padding-top: 30px;
/* IE6 workaround*/
	height: 0;
	overflow: hidden;
}

.centerembed iframe,
.centerembed object,
.centerembed embed {
	margin-left: auto;
	margin-right: auto;
	width: 80%;
	top: 0;
	left: 0;
	height: 100%;
}

And then in the text editor, not the visual editor, making sure to leave the embed URL alone on its own line:

<div class="centerembed">
http://youtube.com/123456
</div>

Different browsers employ different approaches to rendering (displaying) fonts. For example (although I appreciate this may be more technical than you need right now).

Moreover, some fonts only come in certain weights, and different rendering engines will apply different rules to pick a weight if one isn’t specified accurately.

For example, Arial, Helvetica, Georgia, etc. do not have weights other than 400 / “normal” and 700 / “bold”.

I do know that Firefox has had trouble rendering Arial Black. So rather than, as you suspect, IE “bolding” the font, IE may be displaying it correctly and rather Firefox is rendering it in a lighter form.

Try changing from ‘Arial Black’ to Arial 400 for normal paragraph styling and see if there’s consistency across browsers then.

The answer is explained here:

https://wordpress.org/support/topic/fatal-error-call-to-undefined-function-wp_get_current_user-3

It’s likely the last plugin you installed, if you can remember. More info at:

http://herbmiller.me/2014/01/14/fatal-error-call-undefined-function-wp_get_current_user-wp-includescapabilities-php-line-1344/

It doesn’t appear to be bolded, ie,

font-weight: bold;
or
font-weight: 700;
for example.

But it’s just your font selection:
font-family: "Arial Black"