Navbar - active link

Basically i'm trying to make a "active state/currently on" link on my navbar to stand out.
Im doing something wrong here...

Code:

a.mainmenu,:active { color: red; text-decoration: none }

Code:

a.mainmenu:active { color: red; text-decoration: none }


if that doesnt work use

Code:

a.mainmenu active { color: red; text-decoration: none }


Ups i totally missed that comma in the code i posted, anyway
first code you gave me seems it works half the way, when i click it it turns red but doesn't stay that way.

Also forgot, using phbb2


Here is my full CSS sheet if something else is in the way.

Code:

a:link{ text-decoration: none; }

a:active {
text-decoration: none;
}
a:hover {
text-decoration: none;
}

a:link {
text-decoration: none;
}

a:visited {
text-decoration: none;
}



    a {
    text-decoration: none !important;
    }
    a:hover {
    text-decoration: none !important;
    }




a.mainmenu {font-size:11px;}

a.mainmenu {font-weight:bold;}

.poster-profile {text-align:center; font-size:10px;}



.msg span strong {color: #312A5F;}


.chatbox_row_1,
.chatbox_row_2,
.chatbox_row_3,
.chatbox_row_1 has
.chatbox_row_2 has
.chatbox_row_3 a { color: dimgray; }


[href='/faq'] { display: none; }




td.rowpic {
   background-color: #1c1c1c;
   background-image: url("");
   css}
th {
   color: #518AC4;
   font-size: 11px;
   font-weight : bold;
   background-color: #1c1c1c;
   height: 25px;
   background-image: url("");
   padding: 2px 3px;
   }
td.cat,td.catHead,td.catSides,td.catLeft,td.catRight,td.catBottom {
   background-image: url("");
   background-color:#1c1c1c;
    border: #1c1c1c;
    border-style: solid;
    height: 28px;
   }


a.mainmenu:active { color: red; text-decoration: none }



Change the active thing to this:

Code:

a.mainmenu:active { color: red  !important; text-decoration: none  !important; }

I think something is wrong here, i might have explained my problem wrong or i posted a code that has nothing to do with it.

Anyway, here is the image of my navbar compared to a profile menu should help out in visualising the problem.
Image:

As you can see in the image, im looking for a result that profile menu shows, the page im currently on in the profile stays "active" in the gray color, now is it possible for the navbar to have the same/simmilar result.

Also thanks for your time.