Change size of images on product page

I have read some other threads that have talked about this but everything I have tried doesn't work. If you go to my store:
gamingjerseys.com/index.php?option=com_h...me=arbitor&Itemid=99
you will see that the images are rather small. I need to increase the size of the main image to 300x400px and I also want the thumbnails bigger.

I tried editing the CSS and that didn't do anything for me. Please help.

Hi!
I tried to change the small thumbnails size (extra photos).

I replaced

---

div#hikashop_product_left_part img.hikashop_child_image{
margin : 2px;
height:25px;
}

---

with

---

div#hikashop_product_left_part img.hikashop_child_image{
margin : 2px;
height:200px;
width:200px;
}

---

but nothing happens.
How can I change it?

ok
You don t because I change it to previous state. I ll change it again to see it.

i m sorry but it worked now. I don t know what happened, maybe a cashe problem, with firefox. Firefox is going down..