Firefox vs IE issues

I was wondering if anyone knows how to help me with this issue: the fonts appear in the normal size if the site is viewed with Firefox, but they appear huge if viewed with IE. the url is https://www.fernandosouza.org

So, anyone knows? thanks!

here’s the CSS code:

/*
Theme Name: Upstart Blogger Minim
Theme URI: https://www.upstartblogger.com
Description: A minimalist, <b>widgetized</b> theme from <a href="https://www.upstartblogger.com/" title="Upstart Blogger">Upstart Blogger</a>.
Author: Robert Ellis
Author URI: https://www.upstartblogger.com
Version: 0.6
License: Creative Commons Attribution-Share Alike 3.0 (https://creativecommons.org/licenses/by-sa/3.0/). Feel free to make any changes, but please keep a link back to Upstart Blogger in your sidebar or footer.
*/

body {
	background-color: #f0f0f0;
	font-family: Arial, Helvetica, Geneva, sans-serif;
	padding: 20px;
	font-size: .78em;
	line-height: 1.5em;
	color: #444444;
}

#container {
	width: 900px;
}

#sidebar {
	width: 366px;
	float: left;
	font-size: .8em;
	line-height: 1.4em;
	padding: 0 10px 25px 0;
	}

#sidebarleft {
	width:190px;
	float: left;
font-size: 1.1em;
}

#sidebarright {
	width: 135px;
	float: right;
font-size: 1.1em;
}

#footer {
	width:180px;
	float: left;
	clear: both;
	font-size: .64em;
}

#entries {
	width: 468px;
	float: right;
	}

.post {
	margin-bottom: 1em;
}

a {
	color: #6699cc;
	text-decoration: none;
	font-weight: bold;
        font-size: .9em;

}

a:link h3 {
	color: #951400;
	border: none;
}

a:hover {background: #6699cc; font-weight:bold; color: #FFFFFF;}

a:link img {
	border: none;
}

ul {
	list-style: none;
	margin-left: 0px;
	padding-left: 0px;
	margin-top: 0px;
}

li.linkcat {
	list-style-type: none;
}

img {
	border: none;
}

.imgleft {
	float:left;
	margin-right: 10px;
	margin-bottom: 10px;
}

.imgright {
	float: right;
	margin-left: 10px;
	margin-bottom: 10px;
}

img.frame {
	padding: 2px;
	border: solid 1px #DEE4E5;
}

h1 {
	font-size: 1.4em;
        line-height: 1em;
	text-transform: uppercase;
}

h2 {
	font-size: 2em;
	line-height: 1em;
	text-transform: uppercase;
        border-bottom: 1px solid silver;
}

.title {
	border-bottom: 1px solid silver;
}

h3 {
	font-weight: bold;
	font-size: 1.3em;
	text-transform: uppercase;
	margin-bottom: .2em;
	margin-top: 2em;
	letter-spacing: .2em;
	color: #34353e;
	border-bottom: 1px solid silver;
}

.post h3 {
	border-bottom: none;
	letter-spacing: normal;
	margin-bottom: -.5em;
}

h4 {
	font-size: 1em;
        font-style: italic;
	line-height: 1em;

}

blockquote {
	background-color: #f3f3f3;
	padding: 10px;
	margin: 15px 0;
}

/* Begin Comments*/

.comments_tiny {
	color: #b8b8b8;
	border-bottom: 1px solid silver;
}

.alt {
	margin: 0;
	padding: 10px;
	background: #f3f3f3;
}

.commentlist {
	margin-top: 0px;

}

.commentlist li {
	margin: 5px 0 0 0px;

}

.commentlist p {
	margin: 10px 5px 10px 0;
}

#commentform p {
	margin: 5px 0;
}

.nocomments {
	text-align: center;
	margin: 0;
	padding: 0;
}

.commentmetadata {
	margin: 0;
	display: block;
}

li.comment {
	font-weight: bold;
	padding: 10px;
	list-style: none;
}

.commentlist p {
	font-weight: normal;
	line-height: 1.5em;
	text-transform: none;
}

#commentform {
	margin-top: 30px;
}

.commentmetadata {
	font-weight: normal;
}

small, #sidebar ul ul li, #sidebar ul ol li, .nocomments, .postmetadata, blockquote, strike {
	color: #777;
}

.content {
	margin-bottom: 25px;
	padding-left: 5px;
	font-weight: normal;
}

.commentbox {
	width: 100%;
	height: 100px;
}

/* End Comments */