Web server is simply a computer program that dispenses web pages as they are requested. Basically web server is used to host the web sites but there exists other web servers also such as gaming, storage, FTP, email etc.
On-page SEO is the practice of optimizing individual web pages in order to rank higher and earn more relevant traffic in search engines. On-page factors include technical set-up – the quality of your code – textual and visual content and user-friendliness of your site.
SEO friendly URL is helpful to describe your content, help you avoid duplicate content, avoid having your pages trigger spam filters, make your pages easier to share, remember, and type into a browser and help your Web visitors navigate your site.
A canonical tag (aka "rel canonical") is a way of telling search engines that a specific URL represents the master copy of a page. Using the canonical tag prevents problems caused by identical or "duplicate" content appearing on multiple URLs.
Color is important factor to represent your services or products. If you design website for school then design and color combination will different as compare IT services website. Psychology of Color is also big factor to increase conversion.
Firstly you should find toxic links through Google webmaster or paid version of ahref tool, then with the help of Google search console you can request to remove toxic links from their website or you can directly email to website owner to remove your hyperlink.