Many thanks for the links.
The login boxes and the donate button are all <input> elements and the Showkase CSS for <input> elements is being applied to your own <input> elements.
Login boxes:
Change your three <input> lines from:
<input type="text" name="uname" size="15" maxlength="30" style="width: 100px">
<input type="password" name="passwd" size="15" maxlength="30" style="width: 100px">
<input type="submit" name="submit" value="Login" style="width: 65px;">
... to:
<input type="text" name="uname" size="15" maxlength="30" style="width: 100px; display: inline !important;">
<input type="password" name="passwd" size="15" maxlength="30" style="width: 100px; display: inline !important;">
<input type="submit" name="submit" value="Login" style="width: 65px; display: inline !important;">
... (adding display: inline !important; to the 'style' attribute of each one).
Donate button:
Change:
<input alt="" border="0" name="submit" src="https://www.paypal.com/en_US/i/btn/btn_donateCC_LG.gif" type="image" />
... to:
<input alt="" border="0" name="submit" src="https://www.paypal.com/en_US/i/btn/btn_donateCC_LG.gif" type="image" style="width: auto !important;" />
... (adding a 'style' attribute with width: auto !important;).
You could add CSS classes or ids to each of your <input> tags and then add the required CSS rules in your theme's 'custom.css' file but as you would have to modify your custom code anyway (to add the classes or ids), the above suggestions might be the easiest to implement.
I hope this helps.