"I pride myself on offering my clients a truly dynamic and cost effective Websites."
And, is it possible to make it more formal and professional?
Hi Ablil,
Your sentence is fine, formal and professional except for minor grammar errors such as determiner "a" which should not be there since you are referring to websites (plural noun). "Cost-effective" is a compound adjective describing the web site. There should be a hyphen. Perhaps you can use adjectives to describe your "clients" and "websites" more richly. Many advertisers use adjectives to add depth and richness to the product or service they are offering to entice consumers.
An adjective for "clients" could be: valued
Some adjectives for "websites" could be: professional / interactive
I pride myself on offering my valued clients truly dynamic, interactive and cost-effective websites.
Hope this helps.
Cheers, Lance