One of the things that always gets my gander up when I get comps and mockups back from designers is when there are buttons in places that links should be. For whatever reason many designers/UI people really like buttons and put them all over the place. There are pretty defined guidelines for when to use buttons and when to use links and these are often not followed.
How to Design Effective CTA Buttons: 19 Best Practices
Randall Knutson's Instagram, Twitter & Facebook on IDCrawl
Beautiful Examples of Login Forms for Websites and Apps - Designmodo
When to Use Buttons and Links, Wireframing Academy
Getting to Know Buttons and Links, by Sera Tajima
How to Use Link Buttons in Power BI - Zebra BI
Design Decision: Welcome Tab vs. Primer – Signal v. Noise
5 Web Design Tips for an Outstanding Site
Button Design Guide: Get Site Visitors to Click On Your Buttons
Which CTA Button Color Converts the Best?