Uh oh, I think I broke my site.
 

Sorry abou this yet another issue - I think I've broke my site again. I was attempting to edit the theme, but when I reloaded my site, this popped up:
Fatal error: Uncaught exception 'SmartyException' with message 'unable to write file /home/wallie12/public_html/templates/compile/wrt53024c1dbd2e70.20765048' in /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_write_file.php:44 Stack trace: #0 /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_template.php(201): Smarty_Internal_Write_File::writeFile('/home/wallie12/...', '<?php /* Smarty...', Object(Template)) #1 /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_templatebase.php(164): Smarty_Internal_Template->compileTemplateSource() #2 /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_templatebase.php(374): Smarty_Internal_TemplateBase->fetch('template.tpl', NULL, NULL, NULL, true) #3 /home/wallie12/public_html/classes/class_frame.php(226): Smarty_Internal_TemplateBase->display('template.tpl') #4 /home/wallie12/public_html/classes/class_mysidia.php(449): Frame->render() #5 /home/wallie12/public_html/index.php(86): Mysidia->output() #6 /home/wallie12/public_html/ in /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_write_file.php on line 44

Don't worry, I am the same way. I'm sure the amazing coders here can help you out. In the future though, you might want to save a back-up before doing anything major. That way, you can always revert it.

What was the last thing you did, exactly? What were you trying to do?

When modifying anything it should always be done one step at a time, one line at a time. Save. View. Catastrophic failure? Undo. Save. Problem averted. If you don't know what caused the problem down to the wire, you're making modifications in sweeps that are too large. Undo things as you did them, in order, until it's working. That's the best general troubleshooting advice I can give, other than to keep backups!

Pretty much, with an error like that and you don't know what you messed with to cause it, the best way is to go back a version until it works again

Re
 

The funny thing is, I didn't change any code at all - I just changed the copyright year from 2013 to 2014. When it didn't work, I changed it back but...

Are you sure that's the only thing you changed? How did you change it?

Re
 

I just deleted 2013 and replaced it with 2014.
Edit: ok, I just realized that none of the other themes work either... I think it has something to do with the folder...

Empty the /compile folder and the themes will recompile, see if it works.

Re
 

Thanks, I tried it, but now I'm getting this:
Fatal error: Uncaught exception 'SmartyException' with message 'Unable to load template file 'template.tpl'' in /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_templatebase.php:127 Stack trace: #0 /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_templatebase.php(374): Smarty_Internal_TemplateBase->fetch('template.tpl', NULL, NULL, NULL, true) #1 /home/wallie12/public_html/classes/class_frame.php(226): Smarty_Internal_TemplateBase->display('template.tpl') #2 /home/wallie12/public_html/classes/class_mysidia.php(449): Frame->render() #3 /home/wallie12/public_html/index.php(86): Mysidia->output() #4 /home/wallie12/public_html/index.php(90): IndexController::main() #5 {main} thrown in /home/wallie12/public_html/inc/smarty/sysplugins/smarty_internal_templatebase.php on line 127

Umm your theme does not have a template.tpl file? Did you remove or rename it?