Blended Learning Toolkit
A benjanefitness.com resource for designing blended learning resources
If you are hyperlinking to an external URL on a page and this link is one of the main tasks for the student to undertake it should probably be visually unavoidable or obvious and to do this an image of the destination or embedded live version of the destination should be centre on the page.
To do this you could use the snip tool in Windows to create an image, save it on to your computer and then upload to the page (centre it, resize it if needed). Once on the page you can highlight it, press "ctrl K" and then add the destination URL so that any viewers can click the image and go to the page (choose the "open in a new tab" option). It's quite good practice to also include the URL as well unless it's really long and in that case you could create a hyperlink in the text (also using ctrl K when you've highlighted the text).
Passing/supplementary or secondary links could be hyperlinked to in the text. This could also work for extension work for better students or catch-up work for the weaker ones (i.e. look back at last weeks link)