visited link colour doesn't show

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CSS

Hello! Actually I am using the following css in my asp.net project.Everything is working fine except the visited link.I have a lots of link and they are not displaying the visited link color. how to resolve it? and yes when i click on some other link i want the previous link to retain it's previous colour.
Any help would be appreciated. Thanks in advance!

a:link {color:#3333FF;}   

a:hover {color:#FF00FF;font-size:150%;text-decoration:underline;background:yellow;} 

a:active {color:YELLOW;} 

a:visited {color:red;}