We need to disable URL validation here.
1. Open \app\design\install\default\default\template\install\config.phtml
2. Open file in your text editor and find the textbox where the base url is entered.
It will be around line no 50.
3. Remove "validate-url" from its class and save the file.
<input type="text" name="config[unsecure_base_url]" id="base_url" value="<?php echo $this->getFormData()->getUnsecureBaseUrl() ?>" title="<?php echo Mage::helper('core')->quoteEscape($this->__('Base URL')) ?>" class="required-entry validate-url input-text" />
4. After remove "validate-url" from its class. Now looks like:
<input type="text" name="config[unsecure_base_url]" id="base_url" value="<?php echo $this->getFormData()->getUnsecureBaseUrl() ?>" title="<?php echo Mage::helper('core')->quoteEscape($this->__('Base URL')) ?>" class="required-entry input-text" />
5. Now you can continue the installation
