Sub Menu Sensitive In Chrome But Fine In Firefox - css

Question

I'm only a year in to Web Design. I've been learning menus at Lynda.com and specifically have a problem creating a sub menu.
I've made the sub menu how I want it, however when I flick between the list items on my menu they change over too quickly.
See on the picture below:
http://s22.postimg.org/699f35hm9/macca_travel.png
If you look at the position of the cursor, it is still on the 'About' tab, but the 'Blog' hover has lit up and has been selected.
The two sections with sub menus are the 'Blog' tab and the 'Photos' tab. These two tabs don't cross over smoothly and I think it's because for whatever reason they're selecting too quickly.
I don't know why :)
Here is my CSS:
#font-face {
font-family: 'telegraficoregular';
src: url('../FONTS/telegrafico-webfont.eot');
src: url('../FONTS/telegrafico-webfont.eot?#iefix') format('embedded-opentype'),
url('../FONTS/telegrafico-webfont.woff2') format('woff2'),
url('../FONTS/telegrafico-webfont.woff') format('woff'),
url('../FONTS/telegrafico-webfont.ttf') format('truetype'),
url('../FONTS/telegrafico-webfont.svg#telegraficoregular') format('svg');
font-weight: normal;
font-style: normal;
}
.cf:after {
content: "";
display: table;
clear: both;
}
html, body, head, nav, article, aside, section, h3, h4, footer, ul, li {
margin: 0;
padding: 0;
}
/*Global Styles*/
html {
background: white;
margin: 0;
padding: 0;
}
body {
width: 100%;
height: 1200px;
margin: 0 auto;
padding: 0;
background: white;
font-family: serif, arial, helvetica, georgia;
font-size: 16px;
color: black;
}
h1 {
font-family: telegraficoregular;
font-size: 3em;
color: white;
padding: 0;
margin:0;
text-align: center;
}
h2 {
font-family: telegraficoregular;
font-size: 1em;
font-style: italic;
color: white;
padding: 0;
margin: 0;
text-align: center;
}
p {
font-family: serif;
font-size: 1.1em;
color: black;
text-align:left;
padding-left:70px;
}
h4 + p {
font-family: serif;
font-size: 1.1em;
color: black;
text-align:left;
padding-left:70px;
padding-top: 10px;
}
/*Nav Styles */
header {
background:#6593b5;
width: 100%;
height: 160px;
margin:0 auto;
}
nav {
background: black;
height: 2em;
}
nav ul li {
float: left;
}
nav ul li a {
display: block;
padding:0 2em;
line-height: 2em;
color: white;
font-family: telegraficoregular;
text-decoration: none;
}
li, ul {
position: relative;
margin: 0;
padding: 0;
}
ul.SubMenu {
float: none;
width: auto;
height: auto;
list-style: none;
background: black;
color: white;
position: absolute;
left: -9000em;
}
ul.SubMenu li{
float: none;
}
ul.SubMenu li a{
display:block;
border-bottom: 1px solid white;
padding: .2em 2em;
white-space: nowrap;
}
li:hover ul {
left: 0;
}
li:hover ul {
left: 0;
}
/* Article Styles */
article {
width: 896px;
padding: 32px;
}
/*Section Styles */
section.China {
text-align: center;
margin: 80px auto;
padding: 20px;
}
section h3 {
font-family: telegraficoregular;
font-size: 2em;
border-bottom: 1px solid black;
padding: 5px;
}
section h4 {
font-family: telegraficoregular;
font-size: 1.4em;
padding-top: 60px;
padding-left: 70px;
text-align: left;
text-decoration: underline;
}
section.China img {
position: relative;
top: 20px;
border-radius: 5px;
}
section.Australia {
text-align: center;
margin: 20px auto;
padding: 20px;
}
section.Australia img {
position: relative;
top: 20px;
border-radius: 5px;
}
section.Thailand {
text-align: center;
margin: 20px auto;
padding: 20px;
}
section.Thailand img {
position: relative;
top: 20px;
border-radius: 5px;
}
/* Link Styles*/
a:hover {
color: orange;
height: 32px;
background: black;
}
ul.SubMenu li a:hover {
background: orange;
color: white;
}
/* About Styles */
#AboutContent{
width: 960px;
height: 1200px;
margin: 0 auto;
padding: 0;
background: white;
font-family: serif, arial, helvetica, georgia;
font-size: 16px;
color: black;
}
#AboutHeader {
text-align: center;
margin: 20px auto;
padding: 20px;
}
#AboutHeader img {
display: block;
margin: 0 auto;
text-align: center;
}
#AboutHeader h2 {
font-family: telegraficoregular;
font-size: 1.5em;
text-decoration: underline;
color: black;
padding: 0;
margin-top: 20px;
text-align: center;
}
h2 + img {
position: relative;
top: 50px;
border-radius: 5px;
}
#AboutHeader p {
font-family: serif;
font-size: 1.1em;
color: black;
text-align:left;
padding:50px 0 0 100px;
}
/*Photos Content */
#PhotoContent{
width: 960px;
height:auto;
margin: 0 auto;
padding: 0;
background: white;
font-family: serif, arial, helvetica, georgia;
font-size: 16px;
color: black;
}
/* Photos Gallery */
#ChinaPhotos {
width: 960px;
height:1200px;
margin: 0 auto;
padding: 0;
background: white;
font-family: serif, arial, helvetica, georgia;
font-size: 16px;
color: black;
}
#ChinaPhotos h3 {
font-family: telegraficoregular;
font-size: 2em;
border-bottom: 1px solid black;
padding: 5px;
text-align: center;
margin-top: 20px;
}
#ChinaPhotos img {
margin-top: 20px;
border: 1px solid black;
}
#ChinaPhotos a .Thumb:hover {
width: 320px;
height: 240px;
}
/* Container Styles */
#Content {
width: 960px;
height: auto;
margin: 0 auto;
padding: 0;
background: white;
font-family: serif, arial, helvetica, georgia;
font-size: 16px;
color: black;
}
/* Footer Styles */
.Footer {
width: 100%;
height: 160px;
background: black;
}
.Footer p {
font-family: telegraficoregular;
color: white;
font-style: italic;
line-height: 160px;
text-align: center;
}
Thanks Joe

Answer 1

Add the following to each section of your CSS:
ul.SubMenu {
margin-top: 2em;
}
nav ul li a {
float: left;
}
nav ul li {
display: block;
}