diff --git a/cmd/wp-go-static/commands/root.go b/cmd/wp-go-static/commands/root.go
index 9389909..c5a6979 100644
--- a/cmd/wp-go-static/commands/root.go
+++ b/cmd/wp-go-static/commands/root.go
@@ -3,6 +3,7 @@ package commands
 import (
 	"crypto/tls"
 	"fmt"
+	"log"
 	"net/http"
 	"net/url"
 	"regexp"
@@ -70,21 +71,17 @@ func init() {
 	RootCmd.PersistentFlags().String("cache", "", "Cache directory")
 	RootCmd.PersistentFlags().Bool("parallel", false, "Fetch in parallel")
 	RootCmd.PersistentFlags().Bool("images", true, "Download images")
+	RootCmd.MarkFlagRequired("url")
 
 	// Bind command-line flags to Viper
-	viper.BindPFlag("dir", RootCmd.PersistentFlags().Lookup("dir"))
-	viper.BindPFlag("url", RootCmd.PersistentFlags().Lookup("url"))
-	viper.BindPFlag("cache", RootCmd.PersistentFlags().Lookup("cache"))
-	viper.BindPFlag("images", RootCmd.PersistentFlags().Lookup("images"))
+	err := viper.BindPFlags(RootCmd.PersistentFlags())
+	if err != nil {
+		log.Fatal(err)
+	}
 
 	viper.AutomaticEnv()
 	viper.EnvKeyReplacer(strings.NewReplacer("-", "_"))
 	viper.SetEnvPrefix("WGS")
-
-	// Execute root command
-	if err := RootCmd.Execute(); err != nil {
-		fmt.Println(err)
-	}
 }
 
 func rootCmdF(command *cobra.Command, args []string) error {
@@ -103,9 +100,9 @@ func rootCmdF(command *cobra.Command, args []string) error {
 
 	scrape.c.Async = parallel
 
-	// Ignore SSL errors
+	// Use a custom TLS config to verify server certificates
 	scrape.c.WithTransport(&http.Transport{
-		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+		TLSClientConfig: &tls.Config{},
 	})
 
 	parsedURL, err := url.Parse(commandURL)
@@ -120,31 +117,44 @@ func rootCmdF(command *cobra.Command, args []string) error {
 	// On every a element which has href attribute call callback
 	scrape.c.OnHTML("a[href]", func(e *colly.HTMLElement) {
 		link := e.Attr("href")
-		scrape.visitURL(e.Request.AbsoluteURL(link))
+		scrape.visitURL(link)
 	})
 
 	// On every link element call callback
 	scrape.c.OnHTML("link[href]", func(e *colly.HTMLElement) {
 		link := e.Attr("href")
-		scrape.visitURL(e.Request.AbsoluteURL(link))
+		scrape.visitURL(link)
 	})
 
 	// On every script element call callback
 	scrape.c.OnHTML("script[src]", func(e *colly.HTMLElement) {
 		link := e.Attr("src")
-		scrape.visitURL(e.Request.AbsoluteURL(link))
+		scrape.visitURL(link)
 	})
 
 	// On every img element call callback
-
 	scrape.c.OnHTML("img", func(e *colly.HTMLElement) {
-		link := e.Attr("src")
-		scrape.visitURL(e.Request.AbsoluteURL(link))
+		src := e.Attr("src")
+		srcSet := e.Attr("srcset")
+		scrape.visitURL(src)
+
+		if srcSet != "" {
+			srcSetList := strings.Split(srcSet, ",")
+			for _, srcSetURL := range srcSetList {
+				srcSetURL = strings.TrimSpace(srcSetURL)
+				innerSrcSet := strings.Split(srcSetURL, " ")[0]
+				if innerSrcSet == "" {
+					continue
+				}
+
+				scrape.visitURL(innerSrcSet)
+			}
+		}
 	})
 
 	// Before making a request print "Visiting ..."
 	scrape.c.OnRequest(func(r *colly.Request) {
-		fmt.Println("Visiting", r.URL.String())
+		log.Println("Visiting", r.URL.String())
 	})
 
 	// On response
@@ -154,7 +164,7 @@ func rootCmdF(command *cobra.Command, args []string) error {
 
 		err := file.SaveFile(r, dir, fileName)
 		if err != nil {
-			fmt.Println(err)
+			log.Println(err)
 			return
 		}
 	})
@@ -172,15 +182,38 @@ func rootCmdF(command *cobra.Command, args []string) error {
 }
 
 func (s *Scrape) visitURL(link string) {
-	// Download image found on page if it hasn't been visited before
+	link = s.getAbsoluteURL(link)
+
+	if link == "" {
+		return
+	}
+
+	u, err := url.Parse(link)
+	if err != nil {
+		log.Printf("Error parsing URL %s: %s", link, err)
+		return
+	}
+
+	if u.Scheme == "" || u.Host == "" {
+		log.Printf("Invalid URL %s", link)
+		return
+	}
+
+	u.Fragment = ""
+
+	link = u.String()
+
+	// Download page if it hasn't been visited before
 	if !s.urlCache.Get(link) {
 		s.urlCache.Add(link)
-		s.c.Visit(link)
+		err := s.c.Visit(link)
+		if err != nil {
+			log.Println(err)
+		}
 	}
 }
 
 func (s *Scrape) parseBody(body []byte) []byte {
-	// Find all URLs in the CSS file
 	cssUrls := regexp.MustCompile(`url\((https?://[^\s]+)\)`).FindAllStringSubmatch(string(body), -1)
 
 	// Download each referenced file if it hasn't been visited before
@@ -208,3 +241,21 @@ func (s *Scrape) parseBody(body []byte) []byte {
 
 	return body
 }
+
+func (s *Scrape) getAbsoluteURL(inputURL string) string {
+	parsedURL, err := url.Parse(inputURL)
+	if err != nil {
+		return ""
+	}
+
+	if parsedURL.IsAbs() {
+		return inputURL
+	}
+
+	baseURL, err := url.Parse(s.domain)
+	if err != nil {
+		return ""
+	}
+
+	return baseURL.ResolveReference(parsedURL).String()
+}