Sticky side menu

[smudgie]

When you click the links of the following site (click quickly if error doesn't occur) the side menu links disappear. Can anyone tell me what might be wrong?

http://www.agtshop.co.uk/acatalog/Watch_Parts_Dept.html

Thanks

[leehack]

The :active pseudo class on the <a> probably has color of text the same as background.