Your site lacks a "robots.txt" file. This file can protect private content from appearing online, save bandwidth, and lower load time on your server. A missing "robots.txt" file also generates additional errors in your apache log whenever robots request one. Read more about the robots.txt file, and how to create one for your site.

Your site lacks a sitemap file. Sitemaps can help robots index your content more thoroughly and quickly. Read more on Google's guidelines for implementing the sitemap protocol.

Your webpage has 9 'img' tags and none of them contain the required 'alt' attribute.

Congratulations! Your page does not use HTML deprecated tags.

Congratulations! Your website is using the correct version of Google Analytics tracking code.

Congratulations! There are no severe JavaScript errors on your web page.

Congratulations! Your HTML size is 25.09 Kb and this is under the average web page size of 33 Kb.
This leads to a faster page loading time than average.

Your page do not use any HTML compression!
You should compress your HTML to reduce your page size and page loading times - this will help your site retain visitors and increase page views. If you were using compression, you could be compressing your HTML size by 67 % - from 25.09 Kb to 8.36 Kb which would further reduce your page loading time.

Your site loading time is around 7.091 seconds and is over the average loading speed which is 5 seconds.

Your page has more than 20 http requests, which can slow down page loading. You can try reducing http requests through various methods such as using text instead of images, using css sprites, using data URIs instead of images, or combining several external files together into one.

Your site is not using expires headers for your images. An expires tag can help speed up the serving of your webpages for users that regularly visit your site and see the same images. Learn more about how to add expires headers to your images.

Congratulations! Your URL doesn't have any redirects (which could potentially cause site indexation issues and site loading delays).

http://matematik.gyldendal.dk and http://www.matematik.gyldendal.dk/ should resolve to the same URL, but currently do not.

Your website is not using https, a secure communication protocol. Even for sites that do not collect senstive customer information, search engines suggest that switching to https is an increasingly good idea and may help improve rankings. Note: if your site relies primarily on adsense income, be aware that using https may be detrimental to ad earnings.

Congratulations! Your webpage does not include email addresses in plaintext.

Your website is not using media queries. You should consider using this technique in order to implement responsive design functionalities.

Your webpage doesn't take the advantages of HTML Microdata specifications in order to markup structured data. View Google's guide for getting started with microdata.

Your webpage does not use the noindex meta tag. This means that your webpage will be read and indexed by search engines.

Your page does not use the canonical link tag.

Your webpage does not use the nofollow meta tag. This means that search engines will crawl all links from your webpage.

Your site lacks a "robots.txt" file. This file can protect private content from appearing online, save bandwidth, and lower load on your server. A missing "robots.txt" file also generates additional errors in your apache log whenever robots request one.

Your DNS server is not using an SPF record. SPF (Sender Policy Framework) allows administrators to specify which hosts are allowed to send mail from a given domain by creating a specific SPF record or TXT record in the Domain Name System (DNS). You can find more information about SPF records here.