diff --git a/src/formatitko/context.py b/src/formatitko/context.py
index d262ec2..24f98ee 100644
--- a/src/formatitko/context.py
+++ b/src/formatitko/context.py
@@ -1,7 +1,7 @@
 
 from panflute import Doc, Div
 import os
-
+import warnings
 
 # This class is used to keep state while transforming the document using
 # transform.py. For the context to be available to the html and TeX generators,
@@ -68,7 +68,7 @@ class Context:
 
 	def set_metadata(self, key: str, value):
 		if key == "language":
-			print("WARN: Setting language this way doesn't propagate to TeX. Either use the Front Matter or specify it additionally using the \\languagexx macro.")
+			warnings.warn("Setting language this way doesn't propagate to TeX. Either use the Front Matter or specify it additionally using the \\languagexx macro.", UserWarning)
 		meta = self.doc.metadata
 		keys = key.split(".")
 		for k in keys[:-1]:
diff --git a/src/formatitko/html_generator.py b/src/formatitko/html_generator.py
index 32e5b2c..ec11a87 100644
--- a/src/formatitko/html_generator.py
+++ b/src/formatitko/html_generator.py
@@ -7,6 +7,7 @@ from typing import Union, Dict
 import re
 import os
 import io
+import warnings
 
 from pygments import highlight
 from pygments.lexers import get_lexer_by_name
@@ -107,6 +108,7 @@ class HTMLGenerator(OutputGenerator):
 		self.generate_simple_block_tag(e, "main", self.common_attributes(e))
 
 	def generate_CodeBlock(self, e: CodeBlock):
+		lexer = None
 		if e.classes and len(e.classes) > 0 and (e.attributes["highlight"] == True or e.attributes["highlight"] == 'True'):
 			# Syntax highlighting using pygments
 			for cl in e.classes:
@@ -116,8 +118,9 @@ class HTMLGenerator(OutputGenerator):
 					continue
 				break
 			else:
-				lexer = None
-				print(f"WARN: Syntax highligher does not have lexer for element with these classes: {e.classes}")
+				warnings.warn(f"Syntax highligher does not have lexer for element with these classes: {e.classes}", UserWarning)
+
+		if lexer:
 			formatter = HtmlFormatter(style=e.attributes["style"])
 			result = highlight(e.text, lexer, formatter)
 			self.writeraw(result)
diff --git a/src/formatitko/images.py b/src/formatitko/images.py
index 421c9e9..f084302 100644
--- a/src/formatitko/images.py
+++ b/src/formatitko/images.py
@@ -7,6 +7,12 @@ from PIL import Image
 class FileInWrongDirError(Exception):
 	pass
 
+class InkscapeError(Exception):
+	pass
+
+class ImageMagickError(Exception):
+	pass
+
 class ImageProcessor:
 	def __init__(self, public_dir: str, web_path: str, cache_dir: str, *lookup_dirs: List[str]):
 		self.public_dir = public_dir
@@ -67,7 +73,7 @@ class ImageProcessor:
 				height_arg = ['--export-height', str(height)] if height is not None else []
 				dpi_arg = ['--export-dpi', str(dpi)] if dpi is not None else []
 				if subprocess.run(['inkscape', full_path, '-o', target_path, *width_arg, *height_arg, *dpi_arg]).returncode != 0:
-					raise Exception(f"Could not convert '{full_path}' to '{format}'")
+					raise InkscapeError(f"Could not convert '{full_path}' to '{format}'")
 			
 			# Convert everything else using ImageMagick.
 			else:
@@ -75,7 +81,7 @@ class ImageProcessor:
 				density_arg = ['-density', str(dpi)] if dpi is not None else []
 				quality_arg = ['-quality', str(quality)] if quality is not None else []
 				if subprocess.run(['convert', *density_arg, full_path, *resize_arg, *quality_arg, target_path]).returncode != 0:
-					raise Exception(f"Could not convert '{full_path}' to '{format}'")
+					raise ImageMagickError(f"Could not convert '{full_path}' to '{format}'")
 
 		return target_name
 
diff --git a/src/formatitko/katex.py b/src/formatitko/katex.py
index d4c9bf5..711b1d3 100644
--- a/src/formatitko/katex.py
+++ b/src/formatitko/katex.py
@@ -9,6 +9,13 @@ from typing import Dict
 class KatexError(Exception):
 	pass
 
+class NPMNotFoundError(Exception):
+	pass
+
+class KatexServerError(Exception):
+	pass
+
+
 class KatexClient:
 	def __init__(self):
 		# Create temporary directory for socket
@@ -24,7 +31,7 @@ class KatexClient:
 				subprocess.run(["npm", "install"], cwd=srcdir+"/katex-server", check=True)
 			except subprocess.CalledProcessError as e:
 				if e.returncode == 127:
-					raise Exception("npm not found. Node.js is required to use KaTeX.")
+					raise NPMNotFoundError("npm not found. Node.js is required to use KaTeX.")
 				else:
 					raise e
 
@@ -34,7 +41,7 @@ class KatexClient:
 		
 		ok = self._server_process.stdout.readline()
 		if ok != b"OK\n":
-			raise Exception("Failed to connect to katex-server")
+			raise KatexServerError("Failed to connect to katex-server")
 
 		self._client.connect(self._socket_file)
 
@@ -49,7 +56,7 @@ class KatexClient:
 		response = json.loads(data)
 
 		if "error" in response:
-			raise Exception(response["error"])
+			raise KatexServerError(response["error"])
 		if "error" in response["results"][0]:
 			raise KatexError(response["results"][0]["error"])
 		else: