Horiz CSS menu: Hover stopped working

menu, CSS

[SanDiegoPaul]

I have simple site I'm working on, using horizontal CSS menus. The menus work but for hover ... I have the style sheet property set to alter the color background and the text color, upon hover. But they stopped working ... please help.

CSS:
#navigation {
font-family: Arial, Helvetica, sans-serif;
font-size: .9em;
}
#navigation ul {
list-style: none;
margin: 0;
padding: 0;
padding-top: 4px;
}

#navigation li {
display: inline;
}
#navigation a:link, #navigation a:visited {
padding: 3px 10px 2px 10px;
color: #FFFFFF;
background-color: #666666;
text-decoration: none;
border: 1px solid #711515;
}
#navigation a: hover {
color: #FFFFFF;
background-color: #0000FF;
}

HTML:
<div id="navigation" align="center">
<ul>
<li><a href="index.htm">Home Page</a></li>
<li><a href="about.htm">About Us</a></li>
<li><a href="clients.htm">Clients</a></li>
<li><a href="contact.htm">Contact Us!</a></li>
</ul></div>

[SanDiegoPaul]

I deleted the style sheet from the web server & reinstalled it... same results. I refreshed my cache in both browsers to no avail.

Am I missing an obvious thing? The menu worked properly before today when I did some property changes on both HTML and CSS. I did a bunch of things so it's not like I can just 'go back' but this is a simple enough menu where I feel like an idiot not being able to figure out what went wrong!

[OPunWide]

Change

#navigation a :hover

to

#navigation a:hover

(remove the space after the a)

[SanDiegoPaul]

Thank you that worked!