One could also switch to the Classic Template. If no errors then you know one of your custom files has the problem. Use the Debug Tool suggested by ElSlozzo to pinpoint the file.

Referring back to post #8 by crato,

(it said that an unexpected '<' found at line 159 in tpl_shopping_cart_default.php)

That does not mean you remove the first '<' you see on line 159. It means there is a coding syntax error and you need to look at "all" the code to see where the actual error is. That is what debugging is all about.