<script>
function startTimer(){
    var x = 3000 //sample time
    //more code to execute timer
}
</script>
<script>
    var x =  NULL; //set time to NULL
</script>
<A ID="content1" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="killTimer();">Home</A>
    <A ID="content2" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="killTimer();">Meet the Crew</A>
    <A ID="content3" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="killTimer();">Contact Us</A>
    <A ID="content4" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="startTimer();">Photos</A>
    <A ID="content5" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="killTimer();">Partners</A>
    <A ID="content6" CLASS="navlink switcher" STYLE="color:#002EB8" onClick="killTimer();">Packages</A>