--- a/dom/canvas/WebGL2ContextFramebuffers.cpp
+++ b/dom/canvas/WebGL2ContextFramebuffers.cpp
@@ -84,17 +84,17 @@ WebGL2Context::FramebufferTextureLayer(G
         fb = mBoundReadFramebuffer;
         break;
 
     default:
         MOZ_CRASH("GFX: Bad target.");
     }
 
     if (!fb)
-        return ErrorInvalidOperation("%a: Xannot modify framebuffer 0.");
+        return ErrorInvalidOperation("%s: Cannot modify framebuffer 0.", funcName);
 
     fb->FramebufferTextureLayer(funcName, attachment, texture, level, layer);
 }
 
 JS::Value
 WebGL2Context::GetFramebufferAttachmentParameter(JSContext* cx,
                                                  GLenum target,
                                                  GLenum attachment,

--- a/dom/canvas/WebGLContextDraw.cpp
+++ b/dom/canvas/WebGLContextDraw.cpp
@@ -863,17 +863,17 @@ WebGLContext::ValidateBufferFetching(con
             maxVertices = 0;
             maxInstances = 0;
             break;
         }
 
         CheckedUint32 checked_maxAllowedCount = ((checked_byteLength - checked_sizeOfLastElement) / vd.actualStride()) + 1;
 
         if (!checked_maxAllowedCount.isValid()) {
-            ErrorInvalidOperation("%s: Integer overflow occured while checking vertex"
+            ErrorInvalidOperation("%s: Integer overflow occurred while checking vertex"
                                   " attrib %u.",
                                   info, attribLoc);
             return false;
         }
 
         if (vd.divisor == 0) {
             maxVertices = std::min(maxVertices, checked_maxAllowedCount.value());
             hasPerVertex = true;

--- a/dom/canvas/WebGLProgram.cpp
+++ b/dom/canvas/WebGLProgram.cpp
@@ -515,17 +515,17 @@ WebGLProgram::BindAttribLocation(GLuint 
 
     if (loc >= mContext->MaxVertexAttribs()) {
         mContext->ErrorInvalidValue("bindAttribLocation: `location` must be less than"
                                     " MAX_VERTEX_ATTRIBS.");
         return;
     }
 
     if (StringBeginsWith(name, NS_LITERAL_STRING("gl_"))) {
-        mContext->ErrorInvalidOperation("bindAttribLocation: Can't set the  location of a"
+        mContext->ErrorInvalidOperation("bindAttribLocation: Can't set the location of a"
                                         " name that starts with 'gl_'.");
         return;
     }
 
     NS_LossyConvertUTF16toASCII asciiName(name);
 
     auto res = mNextLink_BoundAttribLocs.insert({asciiName, loc});