The Welsh Liberal Democrat leader told MPs that his constituency was in the UK top ten for lowest broadband speed.
He said "the number one request" from small firms was improved speed and access.
UK ministers said the "corner had now been turned on rural broadband access".
Speaking in a Westminster Hall debate, Mr Williams said he welcomed the fact that successive governments had recognised the importance of connectivity and that it simply can not be left to the market to decide where access should be.
He said he was disappointed that the target of 96% super-fast broadband access in Wales had not been met but he welcomed the increase to 87%.
Responding for the UK government, Ed Vaizey said a great deal had been achieved on super-fast broadband.
He said the situation had changed from fewer than 1 in 3 homes in Wales having access to super-fast broadband in 2011 to 97% next year.
Mr Vaizey said in that period 55% of homes in Ceredigion had been given access and this would rise to 85% in 2016 and the "corner had now been turned on rural broadband access".
Broadband quality for many small businesses in rural areas could be the difference between "keeping afloat or going under", Ceredigion Liberal Democrat MP Mark Williams has said.