adobe color wheelAdobe Colour Wheel 

broken link checkerBroken Link Check 

free formatter html validatorFreeformatter HTML Validator 

google structured data testingGoogle Structured Data Tester 

html cleanerHTML Cleaner 

Usability HubUsability Hub is a crowd design testing tool.

UseriumUserium is a simple to that catchs common usability problems before user testing.

WirefyWirefy is a tool to help web designers and developers create fast, manageable wireframes that speed up the journey between sketches and final deliverables. This requires a simple workflow and a well-defined collection of atomic elements so that new UIs can be quickly pulled together. It will style, add or remove components as you see fit. With a bit of base knowledge of HTML and CSS, you can start building flexible wireframes without the headache of working through countless calculations. Use Wirefy to build prototypes quickly, then without starting from scratch implement a Wirefy foundation into any additional framework or CMS system for a fully designed deliverable.