Custom Styles Sheets Overruled by local? Styles? and links broken under Shopping Cart Pictograms

Hi everyone,

I am very new to all this, just done two courses on html and css and I am not diving into the wonderful world of wordpress.

I am trying to create a site with a framemarket/gridmarket theme, marketpress is running the background, and I am quite successful in styling headers, footers, branding, buttons etc.

I sometimes do run into problems though, and I don't know where to find the style for a certain element (a button) or how to untangle the deep hierachies of buttons/links/toggles/open/close for the shopping cart symbol as an example.

1)The buttons: a.my_link_buynow, another one is input.mp_button_addcart.

If I style these in the custom.css, there are still some attributes that seem to get set somewhere else, like background and border for instance. According to "firebug" they are set in "/store/products" (http://localhost/store/products) ... but what kind of file is that? Or does that mean that they inherit these attributes globally? I just seem to be able to find where they are set.

2) The other exchange is exchanging the shopping cart for a little pictogram. When I put in the url( ...) and do the text-indent of -9999em, it's all fine (done in custom.css again). I can do the ...:hover too to highlight the button, but the links underneath are gone and I lose the "view cart" and "hide cart" functionality unless I leave the text-indent off. Then the text gets somewhat squeezed on top of the pictogram, it works, but looks naff.

I would be very grateful for any help with this ... and I am sure lots more in the future.

Thanks for your help